diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/CodeGeneration/DefaultDocumentWriter.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/CodeGeneration/DefaultDocumentWriter.cs
index d6fb6742da..294304dd18 100644
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/CodeGeneration/DefaultDocumentWriter.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/CodeGeneration/DefaultDocumentWriter.cs
@@ -297,6 +297,11 @@ namespace Microsoft.AspNetCore.Razor.Language.CodeGeneration
                 Context.NodeWriter.WriteReferenceCapture(Context, node);
             }
 
+            public override void VisitSetKey(SetKeyIntermediateNode node)
+            {
+                Context.NodeWriter.WriteSetKey(Context, node);
+            }
+
             public override void VisitDefault(IntermediateNode node)
             {
                 Context.RenderChildren(node);
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/CodeGeneration/IntermediateNodeWriter.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/CodeGeneration/IntermediateNodeWriter.cs
index c8a3c6659a..d4e49066f9 100644
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/CodeGeneration/IntermediateNodeWriter.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/CodeGeneration/IntermediateNodeWriter.cs
@@ -64,6 +64,11 @@ namespace Microsoft.AspNetCore.Razor.Language.CodeGeneration
             throw new NotSupportedException("This writer does not support components.");
         }
 
+        public virtual void WriteSetKey(CodeRenderingContext context, SetKeyIntermediateNode node)
+        {
+            throw new NotSupportedException("This writer does not support components.");
+        }
+
         public abstract void BeginWriterScope(CodeRenderingContext context, string writer);
 
         public abstract void EndWriterScope(CodeRenderingContext context);
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/ComponentResources.Designer.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/ComponentResources.Designer.cs
index 5d4e39e752..10af5b8063 100644
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/ComponentResources.Designer.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/ComponentResources.Designer.cs
@@ -168,6 +168,15 @@ namespace Microsoft.AspNetCore.Razor.Language {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to Ensures that the component or element will be preserved across renders if (and only if) the supplied key value matches..
+        /// </summary>
+        internal static string KeyTagHelper_Documentation {
+            get {
+                return ResourceManager.GetString("KeyTagHelper_Documentation", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Declares a layout type for the current document..
         /// </summary>
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/ComponentResources.resx b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/ComponentResources.resx
index 4a27c934ae..48b636ec27 100644
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/ComponentResources.resx
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/ComponentResources.resx
@@ -153,6 +153,9 @@
   <data name="ImplementsDirective_TypeToken_Name" xml:space="preserve">
     <value>TypeName</value>
   </data>
+  <data name="KeyTagHelper_Documentation" xml:space="preserve">
+    <value>Ensures that the component or element will be preserved across renders if (and only if) the supplied key value matches.</value>
+  </data>
   <data name="LayoutDirective_Description" xml:space="preserve">
     <value>Declares a layout type for the current document.</value>
   </data>
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentDesignTimeNodeWriter.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentDesignTimeNodeWriter.cs
index f18235f463..9b38d73700 100644
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentDesignTimeNodeWriter.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentDesignTimeNodeWriter.cs
@@ -314,6 +314,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                 // builder.OpenComponent<MyComponent>(0);
                 // builder.AddAttribute(1, "Foo", ...);
                 // builder.AddAttribute(2, "ChildContent", ...);
+                // builder.SetKey(someValue);
                 // builder.AddElementCapture(3, (__value) => _field = __value);
                 // builder.CloseComponent();
                 foreach (var typeArgument in node.TypeArguments)
@@ -347,6 +348,11 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                     });
                 }
 
+                foreach (var setKey in node.SetKeys)
+                {
+                    context.RenderNode(setKey);
+                }
+
                 foreach (var capture in node.Captures)
                 {
                     context.RenderNode(capture);
@@ -362,7 +368,8 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                 var attributes = node.Attributes.ToList();
                 var childContents = node.ChildContents.ToList();
                 var captures = node.Captures.ToList();
-                var remaining = attributes.Count + childContents.Count + captures.Count;
+                var setKeys = node.SetKeys.ToList();
+                var remaining = attributes.Count + childContents.Count + captures.Count + setKeys.Count;
 
                 context.CodeWriter.Write(node.TypeInferenceNode.FullTypeName);
                 context.CodeWriter.Write(".");
@@ -406,6 +413,20 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                     }
                 }
 
+                for (var i = 0; i < setKeys.Count; i++)
+                {
+                    context.CodeWriter.Write("-1");
+                    context.CodeWriter.Write(", ");
+
+                    WriteSetKeyInnards(context, setKeys[i]);
+
+                    remaining--;
+                    if (remaining > 0)
+                    {
+                        context.CodeWriter.Write(", ");
+                    }
+                }
+
                 for (var i = 0; i < captures.Count; i++)
                 {
                     context.CodeWriter.Write("-1");
@@ -717,6 +738,42 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
             _scopeStack.CloseScope(context);
         }
 
+        public override void WriteSetKey(CodeRenderingContext context, SetKeyIntermediateNode node)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            if (node == null)
+            {
+                throw new ArgumentNullException(nameof(node));
+            }
+
+            // Looks like:
+            //
+            // builder.SetKey(_keyValue);
+
+            var codeWriter = context.CodeWriter;
+
+            codeWriter
+                .WriteStartMethodInvocation($"{_scopeStack.BuilderVarName}.{ComponentsApi.RenderTreeBuilder.SetKey}");
+            WriteSetKeyInnards(context, node);
+            codeWriter.WriteEndMethodInvocation();
+        }
+
+        private void WriteSetKeyInnards(CodeRenderingContext context, SetKeyIntermediateNode node)
+        {
+            WriteCSharpCode(context, new CSharpCodeIntermediateNode
+            {
+                Source = node.Source,
+                Children =
+                    {
+                        node.KeyValueToken
+                    }
+            });
+        }
+
         public override void WriteReferenceCapture(CodeRenderingContext context, ReferenceCaptureIntermediateNode node)
         {
             if (context == null)
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentKeyLoweringPass.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentKeyLoweringPass.cs
new file mode 100644
index 0000000000..7dad9740d5
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentKeyLoweringPass.cs
@@ -0,0 +1,76 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Razor.Language.Intermediate;
+
+namespace Microsoft.AspNetCore.Razor.Language.Components
+{
+    internal class ComponentKeyLoweringPass : ComponentIntermediateNodePassBase, IRazorOptimizationPass
+    {
+        // Run after component lowering pass
+        public override int Order => 50;
+
+        protected override void ExecuteCore(RazorCodeDocument codeDocument, DocumentIntermediateNode documentNode)
+        {
+            if (!IsComponentDocument(documentNode))
+            {
+                return;
+            }
+
+            var @namespace = documentNode.FindPrimaryNamespace();
+            var @class = documentNode.FindPrimaryClass();
+            if (@namespace == null || @class == null)
+            {
+                // Nothing to do, bail. We can't function without the standard structure.
+                return;
+            }
+
+            var references = documentNode.FindDescendantReferences<TagHelperPropertyIntermediateNode>();
+            for (var i = 0; i < references.Count; i++)
+            {
+                var reference = references[i];
+                var node = (TagHelperPropertyIntermediateNode)reference.Node;
+
+                if (node.TagHelper.IsKeyTagHelper())
+                {
+                    reference.Replace(RewriteUsage(reference.Parent, node));
+                }
+            }
+        }
+
+        private IntermediateNode RewriteUsage(IntermediateNode parent, TagHelperPropertyIntermediateNode node)
+        {
+            // If we can't get a nonempty attribute value, do nothing because there will
+            // already be a diagnostic for empty values
+            var keyValueToken = DetermineKeyValueToken(node);
+            if (keyValueToken == null)
+            {
+                return node;
+            }
+
+            return new SetKeyIntermediateNode(keyValueToken);
+        }
+
+        private IntermediateToken DetermineKeyValueToken(TagHelperPropertyIntermediateNode attributeNode)
+        {
+            IntermediateToken foundToken = null;
+
+            if (attributeNode.Children.Count == 1)
+            {
+                if (attributeNode.Children[0] is IntermediateToken token)
+                {
+                    foundToken = token;
+                }
+                else if (attributeNode.Children[0] is CSharpExpressionIntermediateNode csharpNode)
+                {
+                    if (csharpNode.Children.Count == 1)
+                    {
+                        foundToken = csharpNode.Children[0] as IntermediateToken;
+                    }
+                }
+            }
+            
+            return !string.IsNullOrWhiteSpace(foundToken?.Content) ? foundToken : null;
+        }
+    }
+}
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentMetadata.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentMetadata.cs
index 17966db799..f57daad348 100644
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentMetadata.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentMetadata.cs
@@ -23,6 +23,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                 tagHelperKind == ChildContent.TagHelperKind ||
                 tagHelperKind == EventHandler.TagHelperKind ||
                 tagHelperKind == Bind.TagHelperKind ||
+                tagHelperKind == Key.TagHelperKind ||
                 tagHelperKind == Ref.TagHelperKind;
         }
 
@@ -116,6 +117,13 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
             public readonly static string TagHelperKind = "Components.EventHandler";
         }
 
+        public static class Key
+        {
+            public readonly static string TagHelperKind = "Components.Key";
+
+            public static readonly string RuntimeName = "Components.None";
+        }
+
         public static class Ref
         {
             public readonly static string TagHelperKind = "Components.Ref";
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentNodeWriter.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentNodeWriter.cs
index 0629f7dc69..ca8704fef0 100644
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentNodeWriter.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentNodeWriter.cs
@@ -160,6 +160,15 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                 index++;
             }
 
+            foreach (var setKey in node.Component.SetKeys)
+            {
+                context.CodeWriter.WriteStartInstanceMethodInvocation("builder", ComponentsApi.RenderTreeBuilder.SetKey);
+                context.CodeWriter.Write(parameters[index].parameterName);
+                context.CodeWriter.WriteEndMethodInvocation();
+
+                index++;
+            }
+
             foreach (var capture in node.Component.Captures)
             {
                 context.CodeWriter.WriteStartInstanceMethodInvocation("builder", capture.IsComponentCapture ? ComponentsApi.RenderTreeBuilder.AddComponentReferenceCapture : ComponentsApi.RenderTreeBuilder.AddElementReferenceCapture);
@@ -200,6 +209,11 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                     p.Add(($"__seq{p.Count}", typeName, $"__arg{p.Count}"));
                 }
 
+                foreach (var capture in node.Component.SetKeys)
+                {
+                    p.Add(($"__seq{p.Count}", "object", $"__arg{p.Count}"));
+                }
+
                 foreach (var capture in node.Component.Captures)
                 {
                     // The capture type name should already contain the global:: prefix.
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentRuntimeNodeWriter.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentRuntimeNodeWriter.cs
index 83d1c2941f..a3224213a9 100644
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentRuntimeNodeWriter.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentRuntimeNodeWriter.cs
@@ -190,6 +190,11 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                 context.RenderNode(attribute);
             }
 
+            foreach (var setKey in node.SetKeys)
+            {
+                context.RenderNode(setKey);
+            }
+
             foreach (var capture in node.Captures)
             {
                 context.RenderNode(capture);
@@ -317,6 +322,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                 // builder.OpenComponent<MyComponent>(0);
                 // builder.AddAttribute(1, "Foo", ...);
                 // builder.AddAttribute(2, "ChildContent", ...);
+                // builder.SetKey(someValue);
                 // builder.AddElementCapture(3, (__value) => _field = __value);
                 // builder.CloseComponent();
 
@@ -344,6 +350,11 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                     context.RenderNode(childContent);
                 }
 
+                foreach (var setKey in node.SetKeys)
+                {
+                    context.RenderNode(setKey);
+                }
+
                 foreach (var capture in node.Captures)
                 {
                     context.RenderNode(capture);
@@ -366,7 +377,8 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                 var attributes = node.Attributes.ToList();
                 var childContents = node.ChildContents.ToList();
                 var captures = node.Captures.ToList();
-                var remaining = attributes.Count + childContents.Count + captures.Count;
+                var setKeys = node.SetKeys.ToList();
+                var remaining = attributes.Count + childContents.Count + captures.Count + setKeys.Count;
 
                 context.CodeWriter.Write(node.TypeInferenceNode.FullTypeName);
                 context.CodeWriter.Write(".");
@@ -410,6 +422,20 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                     }
                 }
                 
+                for (var i = 0; i < setKeys.Count; i++)
+                {
+                    context.CodeWriter.Write((_sourceSequence++).ToString());
+                    context.CodeWriter.Write(", ");
+
+                    WriteSetKeyInnards(context, setKeys[i]);
+
+                    remaining--;
+                    if (remaining > 0)
+                    {
+                        context.CodeWriter.Write(", ");
+                    }
+                }
+
                 for (var i = 0; i < captures.Count; i++)
                 {
                     context.CodeWriter.Write((_sourceSequence++).ToString());
@@ -651,6 +677,32 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
             _scopeStack.CloseScope(context);
         }
 
+        public override void WriteSetKey(CodeRenderingContext context, SetKeyIntermediateNode node)
+        {
+            // Looks like:
+            //
+            // builder.SetKey(_keyValue);
+
+            var codeWriter = context.CodeWriter;
+
+            codeWriter
+                .WriteStartMethodInvocation($"{_scopeStack.BuilderVarName}.{ComponentsApi.RenderTreeBuilder.SetKey}");
+            WriteSetKeyInnards(context, node);
+            codeWriter.WriteEndMethodInvocation();
+        }
+
+        private void WriteSetKeyInnards(CodeRenderingContext context, SetKeyIntermediateNode node)
+        {
+            WriteCSharpCode(context, new CSharpCodeIntermediateNode
+            {
+                Source = node.Source,
+                Children =
+                    {
+                        node.KeyValueToken
+                    }
+            });
+        }
+
         public override void WriteReferenceCapture(CodeRenderingContext context, ReferenceCaptureIntermediateNode node)
         {
             // Looks like:
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentsApi.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentsApi.cs
index 59db7873dd..858dd7169b 100644
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentsApi.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/ComponentsApi.cs
@@ -87,6 +87,8 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
             public static readonly string GetFrames = nameof(GetFrames);
 
             public static readonly string ChildContent = nameof(ChildContent);
+
+            public static readonly string SetKey = nameof(SetKey);
         }
 
         public static class RuntimeHelpers
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/TagHelperDescriptorExtensions.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/TagHelperDescriptorExtensions.cs
index 1bbd8d8ace..8d16b94f9d 100644
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/TagHelperDescriptorExtensions.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Components/TagHelperDescriptorExtensions.cs
@@ -139,6 +139,18 @@ namespace Microsoft.AspNetCore.Razor.Language.Components
                 string.Equals(ComponentMetadata.EventHandler.TagHelperKind, kind);
         }
 
+        public static bool IsKeyTagHelper(this TagHelperDescriptor tagHelper)
+        {
+            if (tagHelper == null)
+            {
+                throw new ArgumentNullException(nameof(tagHelper));
+            }
+
+            return
+                tagHelper.Metadata.TryGetValue(ComponentMetadata.SpecialKindKey, out var kind) &&
+                string.Equals(ComponentMetadata.Key.TagHelperKind, kind);
+        }
+
         public static bool IsRefTagHelper(this TagHelperDescriptor tagHelper)
         {
             if (tagHelper == null)
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Intermediate/ComponentIntermediateNode.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Intermediate/ComponentIntermediateNode.cs
index f3cb7feea0..7b623a0fe9 100644
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Intermediate/ComponentIntermediateNode.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Intermediate/ComponentIntermediateNode.cs
@@ -16,6 +16,8 @@ namespace Microsoft.AspNetCore.Razor.Language.Intermediate
 
         public IEnumerable<ReferenceCaptureIntermediateNode> Captures => Children.OfType<ReferenceCaptureIntermediateNode>();
 
+        public IEnumerable<SetKeyIntermediateNode> SetKeys => Children.OfType<SetKeyIntermediateNode>();
+
         public IEnumerable<ComponentChildContentIntermediateNode> ChildContents => Children.OfType<ComponentChildContentIntermediateNode>();
 
         public override IntermediateNodeCollection Children { get; } = new IntermediateNodeCollection();
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Intermediate/IntermediateNodeVisitor.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Intermediate/IntermediateNodeVisitor.cs
index af4c6c41af..134294394d 100644
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Intermediate/IntermediateNodeVisitor.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Intermediate/IntermediateNodeVisitor.cs
@@ -168,5 +168,10 @@ namespace Microsoft.AspNetCore.Razor.Language.Intermediate
         {
             VisitDefault(node);
         }
+
+        public virtual void VisitSetKey(SetKeyIntermediateNode node)
+        {
+            VisitDefault(node);
+        }
     }
 }
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Intermediate/MarkupElementIntermediateNode.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Intermediate/MarkupElementIntermediateNode.cs
index 7ea2b95882..bf70855bc3 100644
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Intermediate/MarkupElementIntermediateNode.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Intermediate/MarkupElementIntermediateNode.cs
@@ -14,10 +14,13 @@ namespace Microsoft.AspNetCore.Razor.Language.Intermediate
 
         public IEnumerable<ReferenceCaptureIntermediateNode> Captures => Children.OfType<ReferenceCaptureIntermediateNode>();
 
+        public IEnumerable<SetKeyIntermediateNode> SetKeys => Children.OfType<SetKeyIntermediateNode>();
+
         public IEnumerable<IntermediateNode> Body => Children.Where(c =>
         {
             return
                 c as HtmlAttributeIntermediateNode == null &&
+                c as SetKeyIntermediateNode == null &&
                 c as ReferenceCaptureIntermediateNode == null;
         });
 
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Intermediate/SetKeyIntermediateNode.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Intermediate/SetKeyIntermediateNode.cs
new file mode 100644
index 0000000000..507f89c863
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/Intermediate/SetKeyIntermediateNode.cs
@@ -0,0 +1,42 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+
+namespace Microsoft.AspNetCore.Razor.Language.Intermediate
+{
+    public sealed class SetKeyIntermediateNode : IntermediateNode
+    {
+        public SetKeyIntermediateNode(IntermediateToken keyValueToken)
+        {
+            KeyValueToken = keyValueToken ?? throw new ArgumentNullException(nameof(keyValueToken));
+            Source = KeyValueToken.Source;
+        }
+
+        public override IntermediateNodeCollection Children => IntermediateNodeCollection.ReadOnly;
+
+        public IntermediateToken KeyValueToken { get; }
+
+        public override void Accept(IntermediateNodeVisitor visitor)
+        {
+            if (visitor == null)
+            {
+                throw new ArgumentNullException(nameof(visitor));
+            }
+
+            visitor.VisitSetKey(this);
+        }
+
+        public override void FormatNode(IntermediateNodeFormatter formatter)
+        {
+            if (formatter == null)
+            {
+                throw new ArgumentNullException(nameof(formatter));
+            }
+            
+            formatter.WriteContent(KeyValueToken.Content);
+            
+            formatter.WriteProperty(nameof(KeyValueToken), KeyValueToken.Content);
+        }
+    }
+}
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/RazorProjectEngine.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/RazorProjectEngine.cs
index 82ca3509a8..cdc6b9ff4a 100644
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/src/RazorProjectEngine.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/src/RazorProjectEngine.cs
@@ -226,6 +226,7 @@ namespace Microsoft.AspNetCore.Razor.Language
             builder.Features.Add(new ComponentLoweringPass());
             builder.Features.Add(new ComponentScriptTagPass());
             builder.Features.Add(new ComponentEventHandlerLoweringPass());
+            builder.Features.Add(new ComponentKeyLoweringPass());
             builder.Features.Add(new ComponentReferenceCaptureLoweringPass());
             builder.Features.Add(new ComponentBindLoweringPass());
             builder.Features.Add(new ComponentTemplateDiagnosticPass());
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/IntegrationTests/ComponentCodeGenerationTestBase.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/IntegrationTests/ComponentCodeGenerationTestBase.cs
index 7f76f8cdd4..7cbc74266f 100644
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/IntegrationTests/ComponentCodeGenerationTestBase.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/IntegrationTests/ComponentCodeGenerationTestBase.cs
@@ -2724,6 +2724,68 @@ namespace Test
             CompileToAssembly(generated);
         }
 
+        [Fact]
+        public void GenericComponent_WithKey()
+        {
+            // Arrange
+            AdditionalSyntaxTrees.Add(Parse(@"
+using Microsoft.AspNetCore.Components;
+
+namespace Test
+{
+    public class MyComponent<TItem> : ComponentBase
+    {
+        [Parameter] TItem Item { get; set; }
+    }
+}
+"));
+
+            // Act
+            var generated = CompileToCSharp(@"
+<MyComponent TItem=int Item=""3"" key=""_someKey"" />
+
+@functions {
+    private object _someKey = new object();
+}
+");
+
+            // Assert
+            AssertDocumentNodeMatchesBaseline(generated.CodeDocument);
+            AssertCSharpDocumentMatchesBaseline(generated.CodeDocument);
+            CompileToAssembly(generated);
+        }
+
+        [Fact]
+        public void GenericComponent_WithKey_TypeInference()
+        {
+            // Arrange
+            AdditionalSyntaxTrees.Add(Parse(@"
+using Microsoft.AspNetCore.Components;
+
+namespace Test
+{
+    public class MyComponent<TItem> : ComponentBase
+    {
+        [Parameter] TItem Item { get; set; }
+    }
+}
+"));
+
+            // Act
+            var generated = CompileToCSharp(@"
+<MyComponent Item=""3"" key=""_someKey"" />
+
+@functions {
+    private object _someKey = new object();
+}
+");
+
+            // Assert
+            AssertDocumentNodeMatchesBaseline(generated.CodeDocument);
+            AssertCSharpDocumentMatchesBaseline(generated.CodeDocument);
+            CompileToAssembly(generated);
+        }
+
         [Fact]
         public void GenericComponent_WithComponentRef()
         {
@@ -2831,6 +2893,106 @@ namespace Test.Shared
 
         #endregion
 
+        #region Key
+
+        [Fact]
+        public void Element_WithKey()
+        {
+            // Arrange/Act
+            var generated = CompileToCSharp(@"
+<elem attributebefore=""before"" key=""someObject"" attributeafter=""after"">Hello</elem>
+
+@functions {
+    private object someObject = new object();
+}
+");
+
+            // Assert
+            AssertDocumentNodeMatchesBaseline(generated.CodeDocument);
+            AssertCSharpDocumentMatchesBaseline(generated.CodeDocument);
+            CompileToAssembly(generated);
+        }
+
+        [Fact]
+        public void Element_WithKey_AndOtherAttributes()
+        {
+            // Arrange/Act
+            var generated = CompileToCSharp(@"
+<input type=""text"" data-slider-min=""@Min"" key=""@someObject"" />
+
+@functions {
+        private object someObject = new object();
+
+        [Parameter] protected int Min { get; set; }
+    }
+");
+
+            // Assert
+            AssertDocumentNodeMatchesBaseline(generated.CodeDocument);
+            AssertCSharpDocumentMatchesBaseline(generated.CodeDocument);
+            CompileToAssembly(generated);
+        }
+
+        [Fact]
+        public void Component_WithKey()
+        {
+            // Arrange
+            AdditionalSyntaxTrees.Add(Parse(@"
+using Microsoft.AspNetCore.Components;
+
+namespace Test
+{
+    public class MyComponent : ComponentBase
+    {
+    }
+}
+"));
+
+            // Arrange/Act
+            var generated = CompileToCSharp(@"
+<MyComponent ParamBefore=""before"" key=""someDate.Day"" ParamAfter=""after"" />
+
+@functions {
+    private DateTime someDate = DateTime.Now;
+}
+");
+
+            // Assert
+            AssertDocumentNodeMatchesBaseline(generated.CodeDocument);
+            AssertCSharpDocumentMatchesBaseline(generated.CodeDocument);
+            CompileToAssembly(generated);
+        }
+
+        [Fact]
+        public void Component_WithKey_WithChildContent()
+        {
+            // Arrange
+            AdditionalSyntaxTrees.Add(Parse(@"
+using Microsoft.AspNetCore.Components;
+
+namespace Test
+{
+    public class MyComponent : ComponentBase
+    {
+    }
+}
+"));
+
+            // Arrange/Act
+            var generated = CompileToCSharp(@"
+<MyComponent key=""123 + 456"" SomeProp=""val"">
+    Some <el>further</el> content
+</MyComponent>
+");
+
+            // Assert
+            AssertDocumentNodeMatchesBaseline(generated.CodeDocument);
+            AssertCSharpDocumentMatchesBaseline(generated.CodeDocument);
+            CompileToAssembly(generated);
+        }
+
+        #endregion
+
         #region Ref
 
         [Fact]
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/RazorProjectEngineTest.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/RazorProjectEngineTest.cs
index 65600a9b88..9a5673a70b 100644
--- a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/RazorProjectEngineTest.cs
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/RazorProjectEngineTest.cs
@@ -52,6 +52,7 @@ namespace Microsoft.AspNetCore.Razor.Language.Test
                 feature => Assert.IsType<ComponentEventHandlerLoweringPass>(feature),
                 feature => Assert.IsType<ComponentGenericTypePass>(feature),
                 feature => Assert.IsType<ComponentInjectDirectivePass>(feature),
+                feature => Assert.IsType<ComponentKeyLoweringPass>(feature),
                 feature => Assert.IsType<ComponentLayoutDirectivePass>(feature),
                 feature => Assert.IsType<ComponentLoweringPass>(feature),
                 feature => Assert.IsType<ComponentMarkupBlockPass>(feature),
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Component_WithKey/TestComponent.codegen.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Component_WithKey/TestComponent.codegen.cs
new file mode 100644
index 0000000000..b3049fa6f9
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Component_WithKey/TestComponent.codegen.cs
@@ -0,0 +1,56 @@
+// <auto-generated/>
+#pragma warning disable 1591
+namespace Test
+{
+    #line hidden
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.Components;
+    public class TestComponent : Microsoft.AspNetCore.Components.ComponentBase
+    {
+        #pragma warning disable 219
+        private void __RazorDirectiveTokenHelpers__() {
+        }
+        #pragma warning restore 219
+        #pragma warning disable 0414
+        private static System.Object __o = null;
+        #pragma warning restore 0414
+        #pragma warning disable 1998
+        protected override void BuildRenderTree(Microsoft.AspNetCore.Components.RenderTree.RenderTreeBuilder builder)
+        {
+            __o = "";
+            __o = "";
+            builder.AddAttribute(-1, "ChildContent", (Microsoft.AspNetCore.Components.RenderFragment)((builder2) => {
+            }
+            ));
+            builder.SetKey(
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+                                       someDate.Day
+
+#line default
+#line hidden
+#nullable disable
+            );
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+__o = typeof(MyComponent);
+
+#line default
+#line hidden
+#nullable disable
+        }
+        #pragma warning restore 1998
+#nullable restore
+#line 3 "x:\dir\subdir\Test\TestComponent.cshtml"
+            
+    private DateTime someDate = DateTime.Now;
+
+#line default
+#line hidden
+#nullable disable
+    }
+}
+#pragma warning restore 1591
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Component_WithKey/TestComponent.ir.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Component_WithKey/TestComponent.ir.txt
new file mode 100644
index 0000000000..6b4cf2695b
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Component_WithKey/TestComponent.ir.txt
@@ -0,0 +1,30 @@
+Document - 
+    NamespaceDeclaration -  - Test
+        UsingDirective - (3:1,1 [12] ) - System
+        UsingDirective - (18:2,1 [32] ) - System.Collections.Generic
+        UsingDirective - (53:3,1 [17] ) - System.Linq
+        UsingDirective - (73:4,1 [28] ) - System.Threading.Tasks
+        UsingDirective - (104:5,1 [37] ) - Microsoft.AspNetCore.Components
+        ClassDeclaration -  - public - TestComponent - Microsoft.AspNetCore.Components.ComponentBase - 
+            DesignTimeDirective - 
+            CSharpCode - 
+                IntermediateToken -  - CSharp - #pragma warning disable 0414
+            CSharpCode - 
+                IntermediateToken -  - CSharp - private static System.Object __o = null;
+            CSharpCode - 
+                IntermediateToken -  - CSharp - #pragma warning restore 0414
+            MethodDeclaration -  - protected override - void - BuildRenderTree
+                Component - (0:0,0 [74] x:\dir\subdir\Test\TestComponent.cshtml) - MyComponent
+                    ComponentAttribute -  - ParamBefore - AttributeStructure.DoubleQuotes
+                        HtmlContent - (26:0,26 [6] x:\dir\subdir\Test\TestComponent.cshtml)
+                            IntermediateToken - (26:0,26 [6] x:\dir\subdir\Test\TestComponent.cshtml) - Html - before
+                    SetKey - (39:0,39 [12] x:\dir\subdir\Test\TestComponent.cshtml) - someDate.Day
+                    ComponentAttribute -  - ParamAfter - AttributeStructure.DoubleQuotes
+                        HtmlContent - (65:0,65 [5] x:\dir\subdir\Test\TestComponent.cshtml)
+                            IntermediateToken - (65:0,65 [5] x:\dir\subdir\Test\TestComponent.cshtml) - Html - after
+                HtmlContent - (74:0,74 [4] x:\dir\subdir\Test\TestComponent.cshtml)
+                    IntermediateToken - (74:0,74 [4] x:\dir\subdir\Test\TestComponent.cshtml) - Html - \n\n
+                HtmlContent - (140:4,1 [2] x:\dir\subdir\Test\TestComponent.cshtml)
+                    IntermediateToken - (140:4,1 [2] x:\dir\subdir\Test\TestComponent.cshtml) - Html - \n
+            CSharpCode - (90:2,12 [49] x:\dir\subdir\Test\TestComponent.cshtml)
+                IntermediateToken - (90:2,12 [49] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - \n    private DateTime someDate = DateTime.Now;\n
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Component_WithKey/TestComponent.mappings.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Component_WithKey/TestComponent.mappings.txt
new file mode 100644
index 0000000000..c1f44c953c
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Component_WithKey/TestComponent.mappings.txt
@@ -0,0 +1,14 @@
+Source Location: (39:0,39 [12] x:\dir\subdir\Test\TestComponent.cshtml)
+|someDate.Day|
+Generated Location: (1108:30,39 [12] )
+|someDate.Day|
+
+Source Location: (90:2,12 [49] x:\dir\subdir\Test\TestComponent.cshtml)
+|
+    private DateTime someDate = DateTime.Now;
+|
+Generated Location: (1467:47,12 [49] )
+|
+    private DateTime someDate = DateTime.Now;
+|
+
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Component_WithKey_WithChildContent/TestComponent.codegen.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Component_WithKey_WithChildContent/TestComponent.codegen.cs
new file mode 100644
index 0000000000..014af5ca83
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Component_WithKey_WithChildContent/TestComponent.codegen.cs
@@ -0,0 +1,47 @@
+// <auto-generated/>
+#pragma warning disable 1591
+namespace Test
+{
+    #line hidden
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.Components;
+    public class TestComponent : Microsoft.AspNetCore.Components.ComponentBase
+    {
+        #pragma warning disable 219
+        private void __RazorDirectiveTokenHelpers__() {
+        }
+        #pragma warning restore 219
+        #pragma warning disable 0414
+        private static System.Object __o = null;
+        #pragma warning restore 0414
+        #pragma warning disable 1998
+        protected override void BuildRenderTree(Microsoft.AspNetCore.Components.RenderTree.RenderTreeBuilder builder)
+        {
+            __o = "";
+            builder.AddAttribute(-1, "ChildContent", (Microsoft.AspNetCore.Components.RenderFragment)((builder2) => {
+            }
+            ));
+            builder.SetKey(
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+                  123 + 456
+
+#line default
+#line hidden
+#nullable disable
+            );
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+__o = typeof(MyComponent);
+
+#line default
+#line hidden
+#nullable disable
+        }
+        #pragma warning restore 1998
+    }
+}
+#pragma warning restore 1591
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Component_WithKey_WithChildContent/TestComponent.ir.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Component_WithKey_WithChildContent/TestComponent.ir.txt
new file mode 100644
index 0000000000..7540550b11
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Component_WithKey_WithChildContent/TestComponent.ir.txt
@@ -0,0 +1,31 @@
+Document - 
+    NamespaceDeclaration -  - Test
+        UsingDirective - (3:1,1 [12] ) - System
+        UsingDirective - (18:2,1 [32] ) - System.Collections.Generic
+        UsingDirective - (53:3,1 [17] ) - System.Linq
+        UsingDirective - (73:4,1 [28] ) - System.Threading.Tasks
+        UsingDirective - (104:5,1 [37] ) - Microsoft.AspNetCore.Components
+        ClassDeclaration -  - public - TestComponent - Microsoft.AspNetCore.Components.ComponentBase - 
+            DesignTimeDirective - 
+            CSharpCode - 
+                IntermediateToken -  - CSharp - #pragma warning disable 0414
+            CSharpCode - 
+                IntermediateToken -  - CSharp - private static System.Object __o = null;
+            CSharpCode - 
+                IntermediateToken -  - CSharp - #pragma warning restore 0414
+            MethodDeclaration -  - protected override - void - BuildRenderTree
+                Component - (0:0,0 [95] x:\dir\subdir\Test\TestComponent.cshtml) - MyComponent
+                    ComponentChildContent -  - ChildContent - context
+                        HtmlContent - (44:0,44 [11] x:\dir\subdir\Test\TestComponent.cshtml)
+                            IntermediateToken - (44:0,44 [11] x:\dir\subdir\Test\TestComponent.cshtml) - Html - \n    Some 
+                        MarkupElement - (55:1,9 [16] x:\dir\subdir\Test\TestComponent.cshtml) - el
+                            HtmlContent - (59:1,13 [7] x:\dir\subdir\Test\TestComponent.cshtml)
+                                IntermediateToken - (59:1,13 [7] x:\dir\subdir\Test\TestComponent.cshtml) - Html - further
+                        HtmlContent - (71:1,25 [10] x:\dir\subdir\Test\TestComponent.cshtml)
+                            IntermediateToken - (71:1,25 [10] x:\dir\subdir\Test\TestComponent.cshtml) - Html -  content\n
+                    SetKey - (18:0,18 [9] x:\dir\subdir\Test\TestComponent.cshtml) - 123 + 456
+                    ComponentAttribute -  - SomeProp - AttributeStructure.DoubleQuotes
+                        HtmlContent - (39:0,39 [3] x:\dir\subdir\Test\TestComponent.cshtml)
+                            IntermediateToken - (39:0,39 [3] x:\dir\subdir\Test\TestComponent.cshtml) - Html - val
+                HtmlContent - (95:2,14 [2] x:\dir\subdir\Test\TestComponent.cshtml)
+                    IntermediateToken - (95:2,14 [2] x:\dir\subdir\Test\TestComponent.cshtml) - Html - \n
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Component_WithKey_WithChildContent/TestComponent.mappings.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Component_WithKey_WithChildContent/TestComponent.mappings.txt
new file mode 100644
index 0000000000..e508dba546
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Component_WithKey_WithChildContent/TestComponent.mappings.txt
@@ -0,0 +1,5 @@
+Source Location: (18:0,18 [9] x:\dir\subdir\Test\TestComponent.cshtml)
+|123 + 456|
+Generated Location: (1064:29,18 [9] )
+|123 + 456|
+
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Element_WithKey/TestComponent.codegen.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Element_WithKey/TestComponent.codegen.cs
new file mode 100644
index 0000000000..445881ed56
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Element_WithKey/TestComponent.codegen.cs
@@ -0,0 +1,44 @@
+// <auto-generated/>
+#pragma warning disable 1591
+namespace Test
+{
+    #line hidden
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.Components;
+    public class TestComponent : Microsoft.AspNetCore.Components.ComponentBase
+    {
+        #pragma warning disable 219
+        private void __RazorDirectiveTokenHelpers__() {
+        }
+        #pragma warning restore 219
+        #pragma warning disable 0414
+        private static System.Object __o = null;
+        #pragma warning restore 0414
+        #pragma warning disable 1998
+        protected override void BuildRenderTree(Microsoft.AspNetCore.Components.RenderTree.RenderTreeBuilder builder)
+        {
+            builder.SetKey(
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+                                    someObject
+
+#line default
+#line hidden
+#nullable disable
+            );
+        }
+        #pragma warning restore 1998
+#nullable restore
+#line 3 "x:\dir\subdir\Test\TestComponent.cshtml"
+            
+    private object someObject = new object();
+
+#line default
+#line hidden
+#nullable disable
+    }
+}
+#pragma warning restore 1591
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Element_WithKey/TestComponent.ir.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Element_WithKey/TestComponent.ir.txt
new file mode 100644
index 0000000000..5761655406
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Element_WithKey/TestComponent.ir.txt
@@ -0,0 +1,32 @@
+Document - 
+    NamespaceDeclaration -  - Test
+        UsingDirective - (3:1,1 [12] ) - System
+        UsingDirective - (18:2,1 [32] ) - System.Collections.Generic
+        UsingDirective - (53:3,1 [17] ) - System.Linq
+        UsingDirective - (73:4,1 [28] ) - System.Threading.Tasks
+        UsingDirective - (104:5,1 [37] ) - Microsoft.AspNetCore.Components
+        ClassDeclaration -  - public - TestComponent - Microsoft.AspNetCore.Components.ComponentBase - 
+            DesignTimeDirective - 
+            CSharpCode - 
+                IntermediateToken -  - CSharp - #pragma warning disable 0414
+            CSharpCode - 
+                IntermediateToken -  - CSharp - private static System.Object __o = null;
+            CSharpCode - 
+                IntermediateToken -  - CSharp - #pragma warning restore 0414
+            MethodDeclaration -  - protected override - void - BuildRenderTree
+                MarkupElement - (0:0,0 [83] x:\dir\subdir\Test\TestComponent.cshtml) - elem
+                    HtmlContent - (71:0,71 [5] x:\dir\subdir\Test\TestComponent.cshtml)
+                        IntermediateToken - (71:0,71 [5] x:\dir\subdir\Test\TestComponent.cshtml) - Html - Hello
+                    HtmlAttribute -  - attributebefore=" - "
+                        HtmlAttributeValue - (23:0,23 [6] x:\dir\subdir\Test\TestComponent.cshtml) - 
+                            IntermediateToken - (23:0,23 [6] x:\dir\subdir\Test\TestComponent.cshtml) - Html - before
+                    SetKey - (36:0,36 [10] x:\dir\subdir\Test\TestComponent.cshtml) - someObject
+                    HtmlAttribute -  - attributeafter=" - "
+                        HtmlAttributeValue - (64:0,64 [5] x:\dir\subdir\Test\TestComponent.cshtml) - 
+                            IntermediateToken - (64:0,64 [5] x:\dir\subdir\Test\TestComponent.cshtml) - Html - after
+                HtmlContent - (83:0,83 [4] x:\dir\subdir\Test\TestComponent.cshtml)
+                    IntermediateToken - (83:0,83 [4] x:\dir\subdir\Test\TestComponent.cshtml) - Html - \n\n
+                HtmlContent - (149:4,1 [2] x:\dir\subdir\Test\TestComponent.cshtml)
+                    IntermediateToken - (149:4,1 [2] x:\dir\subdir\Test\TestComponent.cshtml) - Html - \n
+            CSharpCode - (99:2,12 [49] x:\dir\subdir\Test\TestComponent.cshtml)
+                IntermediateToken - (99:2,12 [49] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - \n    private object someObject = new object();\n
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Element_WithKey/TestComponent.mappings.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Element_WithKey/TestComponent.mappings.txt
new file mode 100644
index 0000000000..eb409186f8
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Element_WithKey/TestComponent.mappings.txt
@@ -0,0 +1,14 @@
+Source Location: (36:0,36 [10] x:\dir\subdir\Test\TestComponent.cshtml)
+|someObject|
+Generated Location: (908:25,36 [10] )
+|someObject|
+
+Source Location: (99:2,12 [49] x:\dir\subdir\Test\TestComponent.cshtml)
+|
+    private object someObject = new object();
+|
+Generated Location: (1117:35,12 [49] )
+|
+    private object someObject = new object();
+|
+
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Element_WithKey_AndOtherAttributes/TestComponent.codegen.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Element_WithKey_AndOtherAttributes/TestComponent.codegen.cs
new file mode 100644
index 0000000000..897386b74a
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Element_WithKey_AndOtherAttributes/TestComponent.codegen.cs
@@ -0,0 +1,56 @@
+// <auto-generated/>
+#pragma warning disable 1591
+namespace Test
+{
+    #line hidden
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.Components;
+    public class TestComponent : Microsoft.AspNetCore.Components.ComponentBase
+    {
+        #pragma warning disable 219
+        private void __RazorDirectiveTokenHelpers__() {
+        }
+        #pragma warning restore 219
+        #pragma warning disable 0414
+        private static System.Object __o = null;
+        #pragma warning restore 0414
+        #pragma warning disable 1998
+        protected override void BuildRenderTree(Microsoft.AspNetCore.Components.RenderTree.RenderTreeBuilder builder)
+        {
+            __o = 
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+                                     Min
+
+#line default
+#line hidden
+#nullable disable
+            ;
+            builder.SetKey(
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+                                                someObject
+
+#line default
+#line hidden
+#nullable disable
+            );
+        }
+        #pragma warning restore 1998
+#nullable restore
+#line 3 "x:\dir\subdir\Test\TestComponent.cshtml"
+            
+        private object someObject = new object();
+
+        [Parameter] protected int Min { get; set; }
+    
+
+#line default
+#line hidden
+#nullable disable
+    }
+}
+#pragma warning restore 1591
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Element_WithKey_AndOtherAttributes/TestComponent.ir.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Element_WithKey_AndOtherAttributes/TestComponent.ir.txt
new file mode 100644
index 0000000000..55b45fa3e4
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Element_WithKey_AndOtherAttributes/TestComponent.ir.txt
@@ -0,0 +1,30 @@
+Document - 
+    NamespaceDeclaration -  - Test
+        UsingDirective - (3:1,1 [12] ) - System
+        UsingDirective - (18:2,1 [32] ) - System.Collections.Generic
+        UsingDirective - (53:3,1 [17] ) - System.Linq
+        UsingDirective - (73:4,1 [28] ) - System.Threading.Tasks
+        UsingDirective - (104:5,1 [37] ) - Microsoft.AspNetCore.Components
+        ClassDeclaration -  - public - TestComponent - Microsoft.AspNetCore.Components.ComponentBase - 
+            DesignTimeDirective - 
+            CSharpCode - 
+                IntermediateToken -  - CSharp - #pragma warning disable 0414
+            CSharpCode - 
+                IntermediateToken -  - CSharp - private static System.Object __o = null;
+            CSharpCode - 
+                IntermediateToken -  - CSharp - #pragma warning restore 0414
+            MethodDeclaration -  - protected override - void - BuildRenderTree
+                MarkupElement - (0:0,0 [62] x:\dir\subdir\Test\TestComponent.cshtml) - input
+                    HtmlAttribute -  - type=" - "
+                        HtmlAttributeValue - (13:0,13 [4] x:\dir\subdir\Test\TestComponent.cshtml) - 
+                            IntermediateToken - (13:0,13 [4] x:\dir\subdir\Test\TestComponent.cshtml) - Html - text
+                    HtmlAttribute -  - data-slider-min=" - "
+                        CSharpExpressionAttributeValue - (36:0,36 [4] x:\dir\subdir\Test\TestComponent.cshtml) - 
+                            IntermediateToken - (37:0,37 [3] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - Min
+                    SetKey - (48:0,48 [10] x:\dir\subdir\Test\TestComponent.cshtml) - someObject
+                HtmlContent - (62:0,62 [4] x:\dir\subdir\Test\TestComponent.cshtml)
+                    IntermediateToken - (62:0,62 [4] x:\dir\subdir\Test\TestComponent.cshtml) - Html - \n\n
+                HtmlContent - (191:6,5 [2] x:\dir\subdir\Test\TestComponent.cshtml)
+                    IntermediateToken - (191:6,5 [2] x:\dir\subdir\Test\TestComponent.cshtml) - Html - \n
+            CSharpCode - (78:2,12 [112] x:\dir\subdir\Test\TestComponent.cshtml)
+                IntermediateToken - (78:2,12 [112] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - \n        private object someObject = new object();\n\n        [Parameter] protected int Min { get; set; }\n    
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Element_WithKey_AndOtherAttributes/TestComponent.mappings.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Element_WithKey_AndOtherAttributes/TestComponent.mappings.txt
new file mode 100644
index 0000000000..aa3e3e4fdc
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/Element_WithKey_AndOtherAttributes/TestComponent.mappings.txt
@@ -0,0 +1,23 @@
+Source Location: (37:0,37 [3] x:\dir\subdir\Test\TestComponent.cshtml)
+|Min|
+Generated Location: (900:25,37 [3] )
+|Min|
+
+Source Location: (48:0,48 [10] x:\dir\subdir\Test\TestComponent.cshtml)
+|someObject|
+Generated Location: (1117:34,48 [10] )
+|someObject|
+
+Source Location: (78:2,12 [112] x:\dir\subdir\Test\TestComponent.cshtml)
+|
+        private object someObject = new object();
+
+        [Parameter] protected int Min { get; set; }
+    |
+Generated Location: (1326:44,12 [112] )
+|
+        private object someObject = new object();
+
+        [Parameter] protected int Min { get; set; }
+    |
+
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_WithKey/TestComponent.codegen.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_WithKey/TestComponent.codegen.cs
new file mode 100644
index 0000000000..709829ce9a
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_WithKey/TestComponent.codegen.cs
@@ -0,0 +1,72 @@
+// <auto-generated/>
+#pragma warning disable 1591
+namespace Test
+{
+    #line hidden
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.Components;
+    public class TestComponent : Microsoft.AspNetCore.Components.ComponentBase
+    {
+        #pragma warning disable 219
+        private void __RazorDirectiveTokenHelpers__() {
+        }
+        #pragma warning restore 219
+        #pragma warning disable 0414
+        private static System.Object __o = null;
+        #pragma warning restore 0414
+        #pragma warning disable 1998
+        protected override void BuildRenderTree(Microsoft.AspNetCore.Components.RenderTree.RenderTreeBuilder builder)
+        {
+            __o = typeof(
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+                   int
+
+#line default
+#line hidden
+#nullable disable
+            );
+            __o = Microsoft.AspNetCore.Components.RuntimeHelpers.TypeCheck<int>(
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+                             3
+
+#line default
+#line hidden
+#nullable disable
+            );
+            builder.AddAttribute(-1, "ChildContent", (Microsoft.AspNetCore.Components.RenderFragment)((builder2) => {
+            }
+            ));
+            builder.SetKey(
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+                                     _someKey
+
+#line default
+#line hidden
+#nullable disable
+            );
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+__o = typeof(MyComponent<>);
+
+#line default
+#line hidden
+#nullable disable
+        }
+        #pragma warning restore 1998
+#nullable restore
+#line 3 "x:\dir\subdir\Test\TestComponent.cshtml"
+            
+    private object _someKey = new object();
+
+#line default
+#line hidden
+#nullable disable
+    }
+}
+#pragma warning restore 1591
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_WithKey/TestComponent.ir.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_WithKey/TestComponent.ir.txt
new file mode 100644
index 0000000000..4738739183
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_WithKey/TestComponent.ir.txt
@@ -0,0 +1,28 @@
+Document - 
+    NamespaceDeclaration -  - Test
+        UsingDirective - (3:1,1 [12] ) - System
+        UsingDirective - (18:2,1 [32] ) - System.Collections.Generic
+        UsingDirective - (53:3,1 [17] ) - System.Linq
+        UsingDirective - (73:4,1 [28] ) - System.Threading.Tasks
+        UsingDirective - (104:5,1 [37] ) - Microsoft.AspNetCore.Components
+        ClassDeclaration -  - public - TestComponent - Microsoft.AspNetCore.Components.ComponentBase - 
+            DesignTimeDirective - 
+            CSharpCode - 
+                IntermediateToken -  - CSharp - #pragma warning disable 0414
+            CSharpCode - 
+                IntermediateToken -  - CSharp - private static System.Object __o = null;
+            CSharpCode - 
+                IntermediateToken -  - CSharp - #pragma warning restore 0414
+            MethodDeclaration -  - protected override - void - BuildRenderTree
+                Component - (0:0,0 [49] x:\dir\subdir\Test\TestComponent.cshtml) - MyComponent
+                    ComponentTypeArgument - (19:0,19 [3] x:\dir\subdir\Test\TestComponent.cshtml) - TItem
+                        IntermediateToken - (19:0,19 [3] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - int
+                    ComponentAttribute - (29:0,29 [1] x:\dir\subdir\Test\TestComponent.cshtml) - Item - AttributeStructure.DoubleQuotes
+                        IntermediateToken - (29:0,29 [1] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - 3
+                    SetKey - (37:0,37 [8] x:\dir\subdir\Test\TestComponent.cshtml) - _someKey
+                HtmlContent - (49:0,49 [4] x:\dir\subdir\Test\TestComponent.cshtml)
+                    IntermediateToken - (49:0,49 [4] x:\dir\subdir\Test\TestComponent.cshtml) - Html - \n\n
+                HtmlContent - (113:4,1 [2] x:\dir\subdir\Test\TestComponent.cshtml)
+                    IntermediateToken - (113:4,1 [2] x:\dir\subdir\Test\TestComponent.cshtml) - Html - \n
+            CSharpCode - (65:2,12 [47] x:\dir\subdir\Test\TestComponent.cshtml)
+                IntermediateToken - (65:2,12 [47] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - \n    private object _someKey = new object();\n
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_WithKey/TestComponent.mappings.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_WithKey/TestComponent.mappings.txt
new file mode 100644
index 0000000000..2a8f37b34e
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_WithKey/TestComponent.mappings.txt
@@ -0,0 +1,24 @@
+Source Location: (19:0,19 [3] x:\dir\subdir\Test\TestComponent.cshtml)
+|int|
+Generated Location: (889:25,19 [3] )
+|int|
+
+Source Location: (29:0,29 [1] x:\dir\subdir\Test\TestComponent.cshtml)
+|3|
+Generated Location: (1141:34,29 [1] )
+|3|
+
+Source Location: (37:0,37 [8] x:\dir\subdir\Test\TestComponent.cshtml)
+|_someKey|
+Generated Location: (1497:46,37 [8] )
+|_someKey|
+
+Source Location: (65:2,12 [47] x:\dir\subdir\Test\TestComponent.cshtml)
+|
+    private object _someKey = new object();
+|
+Generated Location: (1854:63,12 [47] )
+|
+    private object _someKey = new object();
+|
+
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_WithKey_TypeInference/TestComponent.codegen.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_WithKey_TypeInference/TestComponent.codegen.cs
new file mode 100644
index 0000000000..1ee445b21c
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_WithKey_TypeInference/TestComponent.codegen.cs
@@ -0,0 +1,73 @@
+// <auto-generated/>
+#pragma warning disable 1591
+namespace Test
+{
+    #line hidden
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.Components;
+    public class TestComponent : Microsoft.AspNetCore.Components.ComponentBase
+    {
+        #pragma warning disable 219
+        private void __RazorDirectiveTokenHelpers__() {
+        }
+        #pragma warning restore 219
+        #pragma warning disable 0414
+        private static System.Object __o = null;
+        #pragma warning restore 0414
+        #pragma warning disable 1998
+        protected override void BuildRenderTree(Microsoft.AspNetCore.Components.RenderTree.RenderTreeBuilder builder)
+        {
+            __Blazor.Test.TestComponent.TypeInference.CreateMyComponent_0(builder, -1, -1, 
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+                   3
+
+#line default
+#line hidden
+#nullable disable
+            , -1, 
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+                           _someKey
+
+#line default
+#line hidden
+#nullable disable
+            );
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+__o = typeof(MyComponent<>);
+
+#line default
+#line hidden
+#nullable disable
+        }
+        #pragma warning restore 1998
+#nullable restore
+#line 3 "x:\dir\subdir\Test\TestComponent.cshtml"
+            
+    private object _someKey = new object();
+
+#line default
+#line hidden
+#nullable disable
+    }
+}
+namespace __Blazor.Test.TestComponent
+{
+    #line hidden
+    internal static class TypeInference
+    {
+        public static void CreateMyComponent_0<TItem>(global::Microsoft.AspNetCore.Components.RenderTree.RenderTreeBuilder builder, int seq, int __seq0, TItem __arg0, int __seq1, object __arg1)
+        {
+        builder.OpenComponent<global::Test.MyComponent<TItem>>(seq);
+        builder.AddAttribute(__seq0, "Item", __arg0);
+        builder.SetKey(__arg1);
+        builder.CloseComponent();
+        }
+    }
+}
+#pragma warning restore 1591
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_WithKey_TypeInference/TestComponent.ir.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_WithKey_TypeInference/TestComponent.ir.txt
new file mode 100644
index 0000000000..3b5cc52c25
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_WithKey_TypeInference/TestComponent.ir.txt
@@ -0,0 +1,29 @@
+Document - 
+    NamespaceDeclaration -  - Test
+        UsingDirective - (3:1,1 [12] ) - System
+        UsingDirective - (18:2,1 [32] ) - System.Collections.Generic
+        UsingDirective - (53:3,1 [17] ) - System.Linq
+        UsingDirective - (73:4,1 [28] ) - System.Threading.Tasks
+        UsingDirective - (104:5,1 [37] ) - Microsoft.AspNetCore.Components
+        ClassDeclaration -  - public - TestComponent - Microsoft.AspNetCore.Components.ComponentBase - 
+            DesignTimeDirective - 
+            CSharpCode - 
+                IntermediateToken -  - CSharp - #pragma warning disable 0414
+            CSharpCode - 
+                IntermediateToken -  - CSharp - private static System.Object __o = null;
+            CSharpCode - 
+                IntermediateToken -  - CSharp - #pragma warning restore 0414
+            MethodDeclaration -  - protected override - void - BuildRenderTree
+                Component - (0:0,0 [39] x:\dir\subdir\Test\TestComponent.cshtml) - MyComponent
+                    ComponentAttribute - (19:0,19 [1] x:\dir\subdir\Test\TestComponent.cshtml) - Item - AttributeStructure.DoubleQuotes
+                        IntermediateToken - (19:0,19 [1] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - 3
+                    SetKey - (27:0,27 [8] x:\dir\subdir\Test\TestComponent.cshtml) - _someKey
+                HtmlContent - (39:0,39 [4] x:\dir\subdir\Test\TestComponent.cshtml)
+                    IntermediateToken - (39:0,39 [4] x:\dir\subdir\Test\TestComponent.cshtml) - Html - \n\n
+                HtmlContent - (103:4,1 [2] x:\dir\subdir\Test\TestComponent.cshtml)
+                    IntermediateToken - (103:4,1 [2] x:\dir\subdir\Test\TestComponent.cshtml) - Html - \n
+            CSharpCode - (55:2,12 [47] x:\dir\subdir\Test\TestComponent.cshtml)
+                IntermediateToken - (55:2,12 [47] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - \n    private object _someKey = new object();\n
+    NamespaceDeclaration -  - __Blazor.Test.TestComponent
+        ClassDeclaration -  - internal static - TypeInference -  - 
+            ComponentTypeInferenceMethod -  - __Blazor.Test.TestComponent.TypeInference - CreateMyComponent_0
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_WithKey_TypeInference/TestComponent.mappings.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_WithKey_TypeInference/TestComponent.mappings.txt
new file mode 100644
index 0000000000..474623cead
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentDesignTimeCodeGenerationTest/GenericComponent_WithKey_TypeInference/TestComponent.mappings.txt
@@ -0,0 +1,19 @@
+Source Location: (19:0,19 [1] x:\dir\subdir\Test\TestComponent.cshtml)
+|3|
+Generated Location: (955:25,19 [1] )
+|3|
+
+Source Location: (27:0,27 [8] x:\dir\subdir\Test\TestComponent.cshtml)
+|_someKey|
+Generated Location: (1125:33,27 [8] )
+|_someKey|
+
+Source Location: (55:2,12 [47] x:\dir\subdir\Test\TestComponent.cshtml)
+|
+    private object _someKey = new object();
+|
+Generated Location: (1482:50,12 [47] )
+|
+    private object _someKey = new object();
+|
+
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Component_WithKey/TestComponent.codegen.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Component_WithKey/TestComponent.codegen.cs
new file mode 100644
index 0000000000..0a8803d967
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Component_WithKey/TestComponent.codegen.cs
@@ -0,0 +1,41 @@
+// <auto-generated/>
+#pragma warning disable 1591
+namespace Test
+{
+    #line hidden
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.Components;
+    public class TestComponent : Microsoft.AspNetCore.Components.ComponentBase
+    {
+        #pragma warning disable 1998
+        protected override void BuildRenderTree(Microsoft.AspNetCore.Components.RenderTree.RenderTreeBuilder builder)
+        {
+            builder.OpenComponent<Test.MyComponent>(0);
+            builder.AddAttribute(1, "ParamBefore", "before");
+            builder.AddAttribute(2, "ParamAfter", "after");
+            builder.SetKey(
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+                                       someDate.Day
+
+#line default
+#line hidden
+#nullable disable
+            );
+            builder.CloseComponent();
+        }
+        #pragma warning restore 1998
+#nullable restore
+#line 3 "x:\dir\subdir\Test\TestComponent.cshtml"
+            
+    private DateTime someDate = DateTime.Now;
+
+#line default
+#line hidden
+#nullable disable
+    }
+}
+#pragma warning restore 1591
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Component_WithKey/TestComponent.ir.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Component_WithKey/TestComponent.ir.txt
new file mode 100644
index 0000000000..021fc0aead
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Component_WithKey/TestComponent.ir.txt
@@ -0,0 +1,19 @@
+Document - 
+    NamespaceDeclaration -  - Test
+        UsingDirective - (3:1,1 [14] ) - System
+        UsingDirective - (18:2,1 [34] ) - System.Collections.Generic
+        UsingDirective - (53:3,1 [19] ) - System.Linq
+        UsingDirective - (73:4,1 [30] ) - System.Threading.Tasks
+        UsingDirective - (104:5,1 [39] ) - Microsoft.AspNetCore.Components
+        ClassDeclaration -  - public - TestComponent - Microsoft.AspNetCore.Components.ComponentBase - 
+            MethodDeclaration -  - protected override - void - BuildRenderTree
+                Component - (0:0,0 [74] x:\dir\subdir\Test\TestComponent.cshtml) - MyComponent
+                    ComponentAttribute -  - ParamBefore - AttributeStructure.DoubleQuotes
+                        HtmlContent - (26:0,26 [6] x:\dir\subdir\Test\TestComponent.cshtml)
+                            IntermediateToken - (26:0,26 [6] x:\dir\subdir\Test\TestComponent.cshtml) - Html - before
+                    SetKey - (39:0,39 [12] x:\dir\subdir\Test\TestComponent.cshtml) - someDate.Day
+                    ComponentAttribute -  - ParamAfter - AttributeStructure.DoubleQuotes
+                        HtmlContent - (65:0,65 [5] x:\dir\subdir\Test\TestComponent.cshtml)
+                            IntermediateToken - (65:0,65 [5] x:\dir\subdir\Test\TestComponent.cshtml) - Html - after
+            CSharpCode - (90:2,12 [49] x:\dir\subdir\Test\TestComponent.cshtml)
+                IntermediateToken - (90:2,12 [49] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - \n    private DateTime someDate = DateTime.Now;\n
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Component_WithKey/TestComponent.mappings.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Component_WithKey/TestComponent.mappings.txt
new file mode 100644
index 0000000000..bdca049e18
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Component_WithKey/TestComponent.mappings.txt
@@ -0,0 +1,14 @@
+Source Location: (39:0,39 [12] x:\dir\subdir\Test\TestComponent.cshtml)
+|someDate.Day|
+Generated Location: (824:21,39 [12] )
+|someDate.Day|
+
+Source Location: (90:2,12 [49] x:\dir\subdir\Test\TestComponent.cshtml)
+|
+    private DateTime someDate = DateTime.Now;
+|
+Generated Location: (1074:32,12 [49] )
+|
+    private DateTime someDate = DateTime.Now;
+|
+
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Component_WithKey_WithChildContent/TestComponent.codegen.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Component_WithKey_WithChildContent/TestComponent.codegen.cs
new file mode 100644
index 0000000000..17c3ae4e46
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Component_WithKey_WithChildContent/TestComponent.codegen.cs
@@ -0,0 +1,37 @@
+// <auto-generated/>
+#pragma warning disable 1591
+namespace Test
+{
+    #line hidden
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.Components;
+    public class TestComponent : Microsoft.AspNetCore.Components.ComponentBase
+    {
+        #pragma warning disable 1998
+        protected override void BuildRenderTree(Microsoft.AspNetCore.Components.RenderTree.RenderTreeBuilder builder)
+        {
+            builder.OpenComponent<Test.MyComponent>(0);
+            builder.AddAttribute(1, "SomeProp", "val");
+            builder.AddAttribute(2, "ChildContent", (Microsoft.AspNetCore.Components.RenderFragment)((builder2) => {
+                builder2.AddMarkupContent(3, "\r\n    Some ");
+                builder2.AddMarkupContent(4, "<el>further</el> content\r\n");
+            }
+            ));
+            builder.SetKey(
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+                  123 + 456
+
+#line default
+#line hidden
+#nullable disable
+            );
+            builder.CloseComponent();
+        }
+        #pragma warning restore 1998
+    }
+}
+#pragma warning restore 1591
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Component_WithKey_WithChildContent/TestComponent.ir.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Component_WithKey_WithChildContent/TestComponent.ir.txt
new file mode 100644
index 0000000000..d5cee0071c
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Component_WithKey_WithChildContent/TestComponent.ir.txt
@@ -0,0 +1,18 @@
+Document - 
+    NamespaceDeclaration -  - Test
+        UsingDirective - (3:1,1 [14] ) - System
+        UsingDirective - (18:2,1 [34] ) - System.Collections.Generic
+        UsingDirective - (53:3,1 [19] ) - System.Linq
+        UsingDirective - (73:4,1 [30] ) - System.Threading.Tasks
+        UsingDirective - (104:5,1 [39] ) - Microsoft.AspNetCore.Components
+        ClassDeclaration -  - public - TestComponent - Microsoft.AspNetCore.Components.ComponentBase - 
+            MethodDeclaration -  - protected override - void - BuildRenderTree
+                Component - (0:0,0 [95] x:\dir\subdir\Test\TestComponent.cshtml) - MyComponent
+                    ComponentChildContent -  - ChildContent - context
+                        HtmlContent - (44:0,44 [11] x:\dir\subdir\Test\TestComponent.cshtml)
+                            IntermediateToken - (44:0,44 [11] x:\dir\subdir\Test\TestComponent.cshtml) - Html - \n    Some 
+                        MarkupBlock -  - <el>further</el> content\n
+                    SetKey - (18:0,18 [9] x:\dir\subdir\Test\TestComponent.cshtml) - 123 + 456
+                    ComponentAttribute -  - SomeProp - AttributeStructure.DoubleQuotes
+                        HtmlContent - (39:0,39 [3] x:\dir\subdir\Test\TestComponent.cshtml)
+                            IntermediateToken - (39:0,39 [3] x:\dir\subdir\Test\TestComponent.cshtml) - Html - val
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Component_WithKey_WithChildContent/TestComponent.mappings.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Component_WithKey_WithChildContent/TestComponent.mappings.txt
new file mode 100644
index 0000000000..d41eee6ea6
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Component_WithKey_WithChildContent/TestComponent.mappings.txt
@@ -0,0 +1,5 @@
+Source Location: (18:0,18 [9] x:\dir\subdir\Test\TestComponent.cshtml)
+|123 + 456|
+Generated Location: (1029:27,18 [9] )
+|123 + 456|
+
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Element_WithKey/TestComponent.codegen.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Element_WithKey/TestComponent.codegen.cs
new file mode 100644
index 0000000000..fd9d0844f6
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Element_WithKey/TestComponent.codegen.cs
@@ -0,0 +1,42 @@
+// <auto-generated/>
+#pragma warning disable 1591
+namespace Test
+{
+    #line hidden
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.Components;
+    public class TestComponent : Microsoft.AspNetCore.Components.ComponentBase
+    {
+        #pragma warning disable 1998
+        protected override void BuildRenderTree(Microsoft.AspNetCore.Components.RenderTree.RenderTreeBuilder builder)
+        {
+            builder.OpenElement(0, "elem");
+            builder.AddAttribute(1, "attributebefore", "before");
+            builder.AddAttribute(2, "attributeafter", "after");
+            builder.SetKey(
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+                                    someObject
+
+#line default
+#line hidden
+#nullable disable
+            );
+            builder.AddContent(3, "Hello");
+            builder.CloseElement();
+        }
+        #pragma warning restore 1998
+#nullable restore
+#line 3 "x:\dir\subdir\Test\TestComponent.cshtml"
+            
+    private object someObject = new object();
+
+#line default
+#line hidden
+#nullable disable
+    }
+}
+#pragma warning restore 1591
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Element_WithKey/TestComponent.ir.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Element_WithKey/TestComponent.ir.txt
new file mode 100644
index 0000000000..5c5902d95a
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Element_WithKey/TestComponent.ir.txt
@@ -0,0 +1,21 @@
+Document - 
+    NamespaceDeclaration -  - Test
+        UsingDirective - (3:1,1 [14] ) - System
+        UsingDirective - (18:2,1 [34] ) - System.Collections.Generic
+        UsingDirective - (53:3,1 [19] ) - System.Linq
+        UsingDirective - (73:4,1 [30] ) - System.Threading.Tasks
+        UsingDirective - (104:5,1 [39] ) - Microsoft.AspNetCore.Components
+        ClassDeclaration -  - public - TestComponent - Microsoft.AspNetCore.Components.ComponentBase - 
+            MethodDeclaration -  - protected override - void - BuildRenderTree
+                MarkupElement - (0:0,0 [83] x:\dir\subdir\Test\TestComponent.cshtml) - elem
+                    HtmlContent - (71:0,71 [5] x:\dir\subdir\Test\TestComponent.cshtml)
+                        IntermediateToken - (71:0,71 [5] x:\dir\subdir\Test\TestComponent.cshtml) - Html - Hello
+                    HtmlAttribute -  - attributebefore=" - "
+                        HtmlAttributeValue - (23:0,23 [6] x:\dir\subdir\Test\TestComponent.cshtml) - 
+                            IntermediateToken - (23:0,23 [6] x:\dir\subdir\Test\TestComponent.cshtml) - Html - before
+                    SetKey - (36:0,36 [10] x:\dir\subdir\Test\TestComponent.cshtml) - someObject
+                    HtmlAttribute -  - attributeafter=" - "
+                        HtmlAttributeValue - (64:0,64 [5] x:\dir\subdir\Test\TestComponent.cshtml) - 
+                            IntermediateToken - (64:0,64 [5] x:\dir\subdir\Test\TestComponent.cshtml) - Html - after
+            CSharpCode - (99:2,12 [49] x:\dir\subdir\Test\TestComponent.cshtml)
+                IntermediateToken - (99:2,12 [49] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - \n    private object someObject = new object();\n
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Element_WithKey/TestComponent.mappings.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Element_WithKey/TestComponent.mappings.txt
new file mode 100644
index 0000000000..0a63f5d85d
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Element_WithKey/TestComponent.mappings.txt
@@ -0,0 +1,14 @@
+Source Location: (36:0,36 [10] x:\dir\subdir\Test\TestComponent.cshtml)
+|someObject|
+Generated Location: (817:21,36 [10] )
+|someObject|
+
+Source Location: (99:2,12 [49] x:\dir\subdir\Test\TestComponent.cshtml)
+|
+    private object someObject = new object();
+|
+Generated Location: (1108:33,12 [49] )
+|
+    private object someObject = new object();
+|
+
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Element_WithKey_AndOtherAttributes/TestComponent.codegen.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Element_WithKey_AndOtherAttributes/TestComponent.codegen.cs
new file mode 100644
index 0000000000..176ad7f171
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Element_WithKey_AndOtherAttributes/TestComponent.codegen.cs
@@ -0,0 +1,52 @@
+// <auto-generated/>
+#pragma warning disable 1591
+namespace Test
+{
+    #line hidden
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.Components;
+    public class TestComponent : Microsoft.AspNetCore.Components.ComponentBase
+    {
+        #pragma warning disable 1998
+        protected override void BuildRenderTree(Microsoft.AspNetCore.Components.RenderTree.RenderTreeBuilder builder)
+        {
+            builder.OpenElement(0, "input");
+            builder.AddAttribute(1, "type", "text");
+            builder.AddAttribute(2, "data-slider-min", 
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+                                     Min
+
+#line default
+#line hidden
+#nullable disable
+            );
+            builder.SetKey(
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+                                                someObject
+
+#line default
+#line hidden
+#nullable disable
+            );
+            builder.CloseElement();
+        }
+        #pragma warning restore 1998
+#nullable restore
+#line 3 "x:\dir\subdir\Test\TestComponent.cshtml"
+            
+        private object someObject = new object();
+
+        [Parameter] protected int Min { get; set; }
+    
+
+#line default
+#line hidden
+#nullable disable
+    }
+}
+#pragma warning restore 1591
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Element_WithKey_AndOtherAttributes/TestComponent.ir.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Element_WithKey_AndOtherAttributes/TestComponent.ir.txt
new file mode 100644
index 0000000000..c4b3b00270
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Element_WithKey_AndOtherAttributes/TestComponent.ir.txt
@@ -0,0 +1,19 @@
+Document - 
+    NamespaceDeclaration -  - Test
+        UsingDirective - (3:1,1 [14] ) - System
+        UsingDirective - (18:2,1 [34] ) - System.Collections.Generic
+        UsingDirective - (53:3,1 [19] ) - System.Linq
+        UsingDirective - (73:4,1 [30] ) - System.Threading.Tasks
+        UsingDirective - (104:5,1 [39] ) - Microsoft.AspNetCore.Components
+        ClassDeclaration -  - public - TestComponent - Microsoft.AspNetCore.Components.ComponentBase - 
+            MethodDeclaration -  - protected override - void - BuildRenderTree
+                MarkupElement - (0:0,0 [62] x:\dir\subdir\Test\TestComponent.cshtml) - input
+                    HtmlAttribute -  - type=" - "
+                        HtmlAttributeValue - (13:0,13 [4] x:\dir\subdir\Test\TestComponent.cshtml) - 
+                            IntermediateToken - (13:0,13 [4] x:\dir\subdir\Test\TestComponent.cshtml) - Html - text
+                    HtmlAttribute -  - data-slider-min=" - "
+                        CSharpExpressionAttributeValue - (36:0,36 [4] x:\dir\subdir\Test\TestComponent.cshtml) - 
+                            IntermediateToken - (37:0,37 [3] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - Min
+                    SetKey - (48:0,48 [10] x:\dir\subdir\Test\TestComponent.cshtml) - someObject
+            CSharpCode - (78:2,12 [112] x:\dir\subdir\Test\TestComponent.cshtml)
+                IntermediateToken - (78:2,12 [112] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - \n        private object someObject = new object();\n\n        [Parameter] protected int Min { get; set; }\n    
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Element_WithKey_AndOtherAttributes/TestComponent.mappings.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Element_WithKey_AndOtherAttributes/TestComponent.mappings.txt
new file mode 100644
index 0000000000..7530b38835
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/Element_WithKey_AndOtherAttributes/TestComponent.mappings.txt
@@ -0,0 +1,18 @@
+Source Location: (48:0,48 [10] x:\dir\subdir\Test\TestComponent.cshtml)
+|someObject|
+Generated Location: (987:29,48 [10] )
+|someObject|
+
+Source Location: (78:2,12 [112] x:\dir\subdir\Test\TestComponent.cshtml)
+|
+        private object someObject = new object();
+
+        [Parameter] protected int Min { get; set; }
+    |
+Generated Location: (1233:40,12 [112] )
+|
+        private object someObject = new object();
+
+        [Parameter] protected int Min { get; set; }
+    |
+
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/GenericComponent_WithKey/TestComponent.codegen.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/GenericComponent_WithKey/TestComponent.codegen.cs
new file mode 100644
index 0000000000..7afcd337b5
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/GenericComponent_WithKey/TestComponent.codegen.cs
@@ -0,0 +1,48 @@
+// <auto-generated/>
+#pragma warning disable 1591
+namespace Test
+{
+    #line hidden
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.Components;
+    public class TestComponent : Microsoft.AspNetCore.Components.ComponentBase
+    {
+        #pragma warning disable 1998
+        protected override void BuildRenderTree(Microsoft.AspNetCore.Components.RenderTree.RenderTreeBuilder builder)
+        {
+            builder.OpenComponent<Test.MyComponent<int>>(0);
+            builder.AddAttribute(1, "Item", Microsoft.AspNetCore.Components.RuntimeHelpers.TypeCheck<int>(
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+                             3
+
+#line default
+#line hidden
+#nullable disable
+            ));
+            builder.SetKey(
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+                                     _someKey
+
+#line default
+#line hidden
+#nullable disable
+            );
+            builder.CloseComponent();
+        }
+        #pragma warning restore 1998
+#nullable restore
+#line 3 "x:\dir\subdir\Test\TestComponent.cshtml"
+            
+    private object _someKey = new object();
+
+#line default
+#line hidden
+#nullable disable
+    }
+}
+#pragma warning restore 1591
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/GenericComponent_WithKey/TestComponent.ir.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/GenericComponent_WithKey/TestComponent.ir.txt
new file mode 100644
index 0000000000..f3c2f8e143
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/GenericComponent_WithKey/TestComponent.ir.txt
@@ -0,0 +1,17 @@
+Document - 
+    NamespaceDeclaration -  - Test
+        UsingDirective - (3:1,1 [14] ) - System
+        UsingDirective - (18:2,1 [34] ) - System.Collections.Generic
+        UsingDirective - (53:3,1 [19] ) - System.Linq
+        UsingDirective - (73:4,1 [30] ) - System.Threading.Tasks
+        UsingDirective - (104:5,1 [39] ) - Microsoft.AspNetCore.Components
+        ClassDeclaration -  - public - TestComponent - Microsoft.AspNetCore.Components.ComponentBase - 
+            MethodDeclaration -  - protected override - void - BuildRenderTree
+                Component - (0:0,0 [49] x:\dir\subdir\Test\TestComponent.cshtml) - MyComponent
+                    ComponentTypeArgument - (19:0,19 [3] x:\dir\subdir\Test\TestComponent.cshtml) - TItem
+                        IntermediateToken - (19:0,19 [3] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - int
+                    ComponentAttribute - (29:0,29 [1] x:\dir\subdir\Test\TestComponent.cshtml) - Item - AttributeStructure.DoubleQuotes
+                        IntermediateToken - (29:0,29 [1] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - 3
+                    SetKey - (37:0,37 [8] x:\dir\subdir\Test\TestComponent.cshtml) - _someKey
+            CSharpCode - (65:2,12 [47] x:\dir\subdir\Test\TestComponent.cshtml)
+                IntermediateToken - (65:2,12 [47] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - \n    private object _someKey = new object();\n
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/GenericComponent_WithKey/TestComponent.mappings.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/GenericComponent_WithKey/TestComponent.mappings.txt
new file mode 100644
index 0000000000..508332c609
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/GenericComponent_WithKey/TestComponent.mappings.txt
@@ -0,0 +1,14 @@
+Source Location: (37:0,37 [8] x:\dir\subdir\Test\TestComponent.cshtml)
+|_someKey|
+Generated Location: (980:28,37 [8] )
+|_someKey|
+
+Source Location: (65:2,12 [47] x:\dir\subdir\Test\TestComponent.cshtml)
+|
+    private object _someKey = new object();
+|
+Generated Location: (1226:39,12 [47] )
+|
+    private object _someKey = new object();
+|
+
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/GenericComponent_WithKey_TypeInference/TestComponent.codegen.cs b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/GenericComponent_WithKey_TypeInference/TestComponent.codegen.cs
new file mode 100644
index 0000000000..6e8d31af45
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/GenericComponent_WithKey_TypeInference/TestComponent.codegen.cs
@@ -0,0 +1,59 @@
+// <auto-generated/>
+#pragma warning disable 1591
+namespace Test
+{
+    #line hidden
+    using System;
+    using System.Collections.Generic;
+    using System.Linq;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.Components;
+    public class TestComponent : Microsoft.AspNetCore.Components.ComponentBase
+    {
+        #pragma warning disable 1998
+        protected override void BuildRenderTree(Microsoft.AspNetCore.Components.RenderTree.RenderTreeBuilder builder)
+        {
+            __Blazor.Test.TestComponent.TypeInference.CreateMyComponent_0(builder, 0, 1, 
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+                   3
+
+#line default
+#line hidden
+#nullable disable
+            , 2, 
+#nullable restore
+#line 1 "x:\dir\subdir\Test\TestComponent.cshtml"
+                           _someKey
+
+#line default
+#line hidden
+#nullable disable
+            );
+        }
+        #pragma warning restore 1998
+#nullable restore
+#line 3 "x:\dir\subdir\Test\TestComponent.cshtml"
+            
+    private object _someKey = new object();
+
+#line default
+#line hidden
+#nullable disable
+    }
+}
+namespace __Blazor.Test.TestComponent
+{
+    #line hidden
+    internal static class TypeInference
+    {
+        public static void CreateMyComponent_0<TItem>(global::Microsoft.AspNetCore.Components.RenderTree.RenderTreeBuilder builder, int seq, int __seq0, TItem __arg0, int __seq1, object __arg1)
+        {
+        builder.OpenComponent<global::Test.MyComponent<TItem>>(seq);
+        builder.AddAttribute(__seq0, "Item", __arg0);
+        builder.SetKey(__arg1);
+        builder.CloseComponent();
+        }
+    }
+}
+#pragma warning restore 1591
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/GenericComponent_WithKey_TypeInference/TestComponent.ir.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/GenericComponent_WithKey_TypeInference/TestComponent.ir.txt
new file mode 100644
index 0000000000..35285b1a16
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/GenericComponent_WithKey_TypeInference/TestComponent.ir.txt
@@ -0,0 +1,18 @@
+Document - 
+    NamespaceDeclaration -  - Test
+        UsingDirective - (3:1,1 [14] ) - System
+        UsingDirective - (18:2,1 [34] ) - System.Collections.Generic
+        UsingDirective - (53:3,1 [19] ) - System.Linq
+        UsingDirective - (73:4,1 [30] ) - System.Threading.Tasks
+        UsingDirective - (104:5,1 [39] ) - Microsoft.AspNetCore.Components
+        ClassDeclaration -  - public - TestComponent - Microsoft.AspNetCore.Components.ComponentBase - 
+            MethodDeclaration -  - protected override - void - BuildRenderTree
+                Component - (0:0,0 [39] x:\dir\subdir\Test\TestComponent.cshtml) - MyComponent
+                    ComponentAttribute - (19:0,19 [1] x:\dir\subdir\Test\TestComponent.cshtml) - Item - AttributeStructure.DoubleQuotes
+                        IntermediateToken - (19:0,19 [1] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - 3
+                    SetKey - (27:0,27 [8] x:\dir\subdir\Test\TestComponent.cshtml) - _someKey
+            CSharpCode - (55:2,12 [47] x:\dir\subdir\Test\TestComponent.cshtml)
+                IntermediateToken - (55:2,12 [47] x:\dir\subdir\Test\TestComponent.cshtml) - CSharp - \n    private object _someKey = new object();\n
+    NamespaceDeclaration -  - __Blazor.Test.TestComponent
+        ClassDeclaration -  - internal static - TypeInference -  - 
+            ComponentTypeInferenceMethod -  - __Blazor.Test.TestComponent.TypeInference - CreateMyComponent_0
diff --git a/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/GenericComponent_WithKey_TypeInference/TestComponent.mappings.txt b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/GenericComponent_WithKey_TypeInference/TestComponent.mappings.txt
new file mode 100644
index 0000000000..0873889778
--- /dev/null
+++ b/src/Razor/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentRuntimeCodeGenerationTest/GenericComponent_WithKey_TypeInference/TestComponent.mappings.txt
@@ -0,0 +1,14 @@
+Source Location: (27:0,27 [8] x:\dir\subdir\Test\TestComponent.cshtml)
+|_someKey|
+Generated Location: (854:26,27 [8] )
+|_someKey|
+
+Source Location: (55:2,12 [47] x:\dir\subdir\Test\TestComponent.cshtml)
+|
+    private object _someKey = new object();
+|
+Generated Location: (1061:36,12 [47] )
+|
+    private object _someKey = new object();
+|
+
diff --git a/src/Razor/Microsoft.CodeAnalysis.Razor/src/CompilerFeatures.cs b/src/Razor/Microsoft.CodeAnalysis.Razor/src/CompilerFeatures.cs
index b42e6b5cc8..b555832cc8 100644
--- a/src/Razor/Microsoft.CodeAnalysis.Razor/src/CompilerFeatures.cs
+++ b/src/Razor/Microsoft.CodeAnalysis.Razor/src/CompilerFeatures.cs
@@ -28,6 +28,7 @@ namespace Microsoft.CodeAnalysis.Razor
                 builder.Features.Add(new ComponentTagHelperDescriptorProvider());
                 builder.Features.Add(new EventHandlerTagHelperDescriptorProvider());
                 builder.Features.Add(new RefTagHelperDescriptorProvider());
+                builder.Features.Add(new KeyTagHelperDescriptorProvider());
 
                 builder.Features.Add(new DefaultTypeNameFeature());
             }
diff --git a/src/Razor/Microsoft.CodeAnalysis.Razor/src/KeyTagHelperDescriptorProvider.cs b/src/Razor/Microsoft.CodeAnalysis.Razor/src/KeyTagHelperDescriptorProvider.cs
new file mode 100644
index 0000000000..7ea05126be
--- /dev/null
+++ b/src/Razor/Microsoft.CodeAnalysis.Razor/src/KeyTagHelperDescriptorProvider.cs
@@ -0,0 +1,77 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.AspNetCore.Razor.Language.Components;
+
+namespace Microsoft.CodeAnalysis.Razor
+{
+    internal class KeyTagHelperDescriptorProvider : ITagHelperDescriptorProvider
+    {
+        // Run after the component tag helper provider
+        public int Order { get; set; } = 1000;
+
+        public RazorEngine Engine { get; set; }
+
+        public void Execute(TagHelperDescriptorProviderContext context)
+        {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            var compilation = context.GetCompilation();
+            if (compilation == null)
+            {
+                return;
+            }
+
+            var renderTreeBuilderType = compilation.GetTypeByMetadataName(ComponentsApi.RenderTreeBuilder.FullTypeName);
+            if (renderTreeBuilderType == null)
+            {
+                // If we can't find RenderTreeBuilder, then just bail. We won't be able to compile the
+                // generated code anyway.
+                return;
+            }
+
+            context.Results.Add(CreateKeyTagHelper());
+        }
+
+        private TagHelperDescriptor CreateKeyTagHelper()
+        {
+            var builder = TagHelperDescriptorBuilder.Create(ComponentMetadata.Key.TagHelperKind, "Key", ComponentsApi.AssemblyName);
+            builder.Documentation = ComponentResources.KeyTagHelper_Documentation;
+
+            builder.Metadata.Add(ComponentMetadata.SpecialKindKey, ComponentMetadata.Key.TagHelperKind);
+            builder.Metadata.Add(TagHelperMetadata.Common.ClassifyAttributesOnly, bool.TrueString);
+            builder.Metadata[TagHelperMetadata.Runtime.Name] = ComponentMetadata.Key.RuntimeName;
+
+            // WTE has a bug in 15.7p1 where a Tag Helper without a display-name that looks like
+            // a C# property will crash trying to create the tooltips.
+            builder.SetTypeName("Microsoft.AspNetCore.Components.Key");
+
+            builder.TagMatchingRule(rule =>
+            {
+                rule.TagName = "*";
+                rule.Attribute(attribute =>
+                {
+                    attribute.Name = "key";
+                });
+            });
+
+            builder.BindAttribute(attribute =>
+            {
+                attribute.Documentation = ComponentResources.KeyTagHelper_Documentation;
+                attribute.Name = "key";
+
+                // WTE has a bug 15.7p1 where a Tag Helper without a display-name that looks like
+                // a C# property will crash trying to create the tooltips.
+                attribute.SetPropertyName("Key");
+                attribute.TypeName = typeof(object).FullName;
+            });
+
+            return builder.Build();
+        }
+    }
+}
diff --git a/src/Razor/Microsoft.CodeAnalysis.Razor/test/KeyTagHelperDescriptorProviderTest.cs b/src/Razor/Microsoft.CodeAnalysis.Razor/test/KeyTagHelperDescriptorProviderTest.cs
new file mode 100644
index 0000000000..ae9288bd19
--- /dev/null
+++ b/src/Razor/Microsoft.CodeAnalysis.Razor/test/KeyTagHelperDescriptorProviderTest.cs
@@ -0,0 +1,88 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Linq;
+using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.AspNetCore.Razor.Language.Components;
+using Xunit;
+
+namespace Microsoft.CodeAnalysis.Razor
+{
+    public class KeyTagHelperDescriptorProviderTest : TagHelperDescriptorProviderTestBase
+    {
+        [Fact]
+        public void Execute_CreatesDescriptor()
+        {
+            // Arrange
+            var context = TagHelperDescriptorProviderContext.Create();
+            context.SetCompilation(BaseCompilation);
+
+            var provider = new KeyTagHelperDescriptorProvider();
+
+            // Act
+            provider.Execute(context);
+
+            // Assert
+            var matches = context.Results.Where(result => result.IsKeyTagHelper());
+            var item = Assert.Single(matches);
+
+            Assert.Empty(item.AllowedChildTags);
+            Assert.Null(item.TagOutputHint);
+            Assert.Empty(item.Diagnostics);
+            Assert.False(item.HasErrors);
+            Assert.Equal(ComponentMetadata.Key.TagHelperKind, item.Kind);
+            Assert.Equal(bool.TrueString, item.Metadata[TagHelperMetadata.Common.ClassifyAttributesOnly]);
+            Assert.Equal(ComponentMetadata.Key.RuntimeName, item.Metadata[TagHelperMetadata.Runtime.Name]);
+            Assert.False(item.IsDefaultKind());
+            Assert.False(item.KindUsesDefaultTagHelperRuntime());
+
+            Assert.Equal(
+                "Ensures that the component or element will be preserved across renders if (and only if) the supplied key value matches.",
+                item.Documentation);
+
+            Assert.Equal("Microsoft.AspNetCore.Components", item.AssemblyName);
+            Assert.Equal("Key", item.Name);
+            Assert.Equal("Microsoft.AspNetCore.Components.Key", item.DisplayName);
+            Assert.Equal("Microsoft.AspNetCore.Components.Key", item.GetTypeName());
+
+            // The tag matching rule for a key is just the attribute name "key"
+            var rule = Assert.Single(item.TagMatchingRules);
+            Assert.Empty(rule.Diagnostics);
+            Assert.False(rule.HasErrors);
+            Assert.Null(rule.ParentTag);
+            Assert.Equal("*", rule.TagName);
+            Assert.Equal(TagStructure.Unspecified, rule.TagStructure);
+
+            var requiredAttribute = Assert.Single(rule.Attributes);
+            Assert.Empty(requiredAttribute.Diagnostics);
+            Assert.Equal("key", requiredAttribute.DisplayName);
+            Assert.Equal("key", requiredAttribute.Name);
+            Assert.Equal(RequiredAttributeDescriptor.NameComparisonMode.FullMatch, requiredAttribute.NameComparison);
+            Assert.Null(requiredAttribute.Value);
+            Assert.Equal(RequiredAttributeDescriptor.ValueComparisonMode.None, requiredAttribute.ValueComparison);
+
+            var attribute = Assert.Single(item.BoundAttributes);
+            Assert.Empty(attribute.Diagnostics);
+            Assert.False(attribute.HasErrors);
+            Assert.Equal(ComponentMetadata.Key.TagHelperKind, attribute.Kind);
+            Assert.False(attribute.IsDefaultKind());
+            Assert.False(attribute.HasIndexer);
+            Assert.Null(attribute.IndexerNamePrefix);
+            Assert.Null(attribute.IndexerTypeName);
+            Assert.False(attribute.IsIndexerBooleanProperty);
+            Assert.False(attribute.IsIndexerStringProperty);
+
+            Assert.Equal(
+                "Ensures that the component or element will be preserved across renders if (and only if) the supplied key value matches.",
+                attribute.Documentation);
+
+            Assert.Equal("key", attribute.Name);
+            Assert.Equal("Key", attribute.GetPropertyName());
+            Assert.Equal("object Microsoft.AspNetCore.Components.Key.Key", attribute.DisplayName);
+            Assert.Equal("System.Object", attribute.TypeName);
+            Assert.False(attribute.IsStringProperty);
+            Assert.False(attribute.IsBooleanProperty);
+            Assert.False(attribute.IsEnum);
+        }
+    }
+}
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common/Language/IntegrationTests/IntermediateNodeWriter.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common/Language/IntegrationTests/IntermediateNodeWriter.cs
index 4ae07f5e8d..c83dbb7c79 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common/Language/IntegrationTests/IntermediateNodeWriter.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.Common/Language/IntegrationTests/IntermediateNodeWriter.cs
@@ -168,6 +168,11 @@ namespace Microsoft.AspNetCore.Razor.Language.IntegrationTests
             WriteContentNode(node, node.IdentifierToken?.Content);
         }
 
+        public override void VisitSetKey(SetKeyIntermediateNode node)
+        {
+            WriteContentNode(node, node.KeyValueToken?.Content);
+        }
+
         void IExtensionIntermediateNodeVisitor<RouteAttributeExtensionNode>.VisitExtension(RouteAttributeExtensionNode node)
         {
             WriteContentNode(node, node.Template);
diff --git a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.ComponentShim/Microsoft.AspNetCore.Components/RenderTree/RenderTreeBuilder.cs b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.ComponentShim/Microsoft.AspNetCore.Components/RenderTree/RenderTreeBuilder.cs
index e07c337a4d..2dfaac26cf 100644
--- a/src/Razor/test/Microsoft.AspNetCore.Razor.Test.ComponentShim/Microsoft.AspNetCore.Components/RenderTree/RenderTreeBuilder.cs
+++ b/src/Razor/test/Microsoft.AspNetCore.Razor.Test.ComponentShim/Microsoft.AspNetCore.Components/RenderTree/RenderTreeBuilder.cs
@@ -103,5 +103,9 @@ namespace Microsoft.AspNetCore.Components.RenderTree
         public void AddComponentReferenceCapture(int sequence, Action<object> componentReferenceCaptureAction)
         {
         }
+
+        public void SetKey(object key)
+        {
+        }
     }
 }
\ No newline at end of file