diff --git a/src/Razor/Microsoft.CodeAnalysis.Razor/src/ComponentDetectionConventions.cs b/src/Razor/Microsoft.CodeAnalysis.Razor/src/ComponentDetectionConventions.cs
new file mode 100644
index 0000000000..214f9e36a4
--- /dev/null
+++ b/src/Razor/Microsoft.CodeAnalysis.Razor/src/ComponentDetectionConventions.cs
@@ -0,0 +1,28 @@
+// 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.CodeAnalysis.Razor
+{
+    internal static class ComponentDetectionConventions
+    {
+        public static bool IsComponent(INamedTypeSymbol symbol, INamedTypeSymbol icomponentSymbol)
+        {
+            if (symbol is null)
+            {
+                throw new ArgumentNullException(nameof(symbol));
+            }
+
+            if (icomponentSymbol is null)
+            {
+                throw new ArgumentNullException(nameof(icomponentSymbol));
+            }
+
+            return
+                symbol.DeclaredAccessibility == Accessibility.Public &&
+                !symbol.IsAbstract &&
+                symbol.AllInterfaces.Contains(icomponentSymbol);
+        }
+    }
+}
diff --git a/src/Razor/Microsoft.CodeAnalysis.Razor/src/ComponentTagHelperDescriptorProvider.cs b/src/Razor/Microsoft.CodeAnalysis.Razor/src/ComponentTagHelperDescriptorProvider.cs
index f160b53a90..ebc1947ca7 100644
--- a/src/Razor/Microsoft.CodeAnalysis.Razor/src/ComponentTagHelperDescriptorProvider.cs
+++ b/src/Razor/Microsoft.CodeAnalysis.Razor/src/ComponentTagHelperDescriptorProvider.cs
@@ -573,10 +573,8 @@ namespace Microsoft.CodeAnalysis.Razor
                     return false;
                 }
 
-                return
-                    symbol.DeclaredAccessibility == Accessibility.Public &&
-                    !symbol.IsAbstract &&
-                    symbol.AllInterfaces.Contains(_symbols.IComponent);
+                var isComponent = ComponentDetectionConventions.IsComponent(symbol, _symbols.IComponent);
+                return isComponent;
             }
         }
     }
diff --git a/src/Razor/Microsoft.NET.Sdk.Razor/src/Sdk/Sdk.Razor.StaticAssets.ProjectSystem.props b/src/Razor/Microsoft.NET.Sdk.Razor/src/Sdk/Sdk.Razor.StaticAssets.ProjectSystem.props
index f54b74ebf4..beb01baa38 100644
--- a/src/Razor/Microsoft.NET.Sdk.Razor/src/Sdk/Sdk.Razor.StaticAssets.ProjectSystem.props
+++ b/src/Razor/Microsoft.NET.Sdk.Razor/src/Sdk/Sdk.Razor.StaticAssets.ProjectSystem.props
@@ -28,8 +28,13 @@ Copyright (c) .NET Foundation. All rights reserved.
   <ItemGroup Condition="'$(EnableDefaultItems)' == 'true' And '$(EnableDefaultContentItems)' == 'true' ">
     <!-- Publish everything under wwwroot, all JSON files, all config files and all Razor files -->
     <Content Include="wwwroot\**" ExcludeFromSingleFile="true" CopyToPublishDirectory="PreserveNewest" Exclude="$(DefaultItemExcludes);$(DefaultExcludesInProjectFolder)" />
-    <Content Include="**\*.config" ExcludeFromSingleFile="true" CopyToOutputDirectory="PreserveNewest" CopyToPublishDirectory="PreserveNewest" Exclude="$(DefaultItemExcludes);$(DefaultExcludesInProjectFolder);$(DefaultWebContentItemExcludes)" />
-    <Content Include="**\*.json" ExcludeFromSingleFile="true" CopyToOutputDirectory="PreserveNewest" CopyToPublishDirectory="PreserveNewest" Exclude="$(DefaultItemExcludes);$(DefaultExcludesInProjectFolder);$(DefaultWebContentItemExcludes)" />
+
+    <Content Include="**\*.config" ExcludeFromSingleFile="true" CopyToOutputDirectory="PreserveNewest" CopyToPublishDirectory="PreserveNewest" Exclude="$(DefaultItemExcludes);$(DefaultExcludesInProjectFolder);$(DefaultWebContentItemExcludes)" Condition="'$(ExcludeConfigFilesFromBuildOutput)'!='true'" />
+    <Content Include="**\*.json" ExcludeFromSingleFile="true" CopyToOutputDirectory="PreserveNewest" CopyToPublishDirectory="PreserveNewest" Exclude="$(DefaultItemExcludes);$(DefaultExcludesInProjectFolder);$(DefaultWebContentItemExcludes)" Condition="'$(ExcludeConfigFilesFromBuildOutput)'!='true'" />
+
+    <!-- When ExcludeConfigFilesFromBuildOutput is set, do not copy .,config, .json files to the build output directory. -->
+    <Content Include="**\*.config" ExcludeFromSingleFile="true" CopyToPublishDirectory="PreserveNewest" Exclude="$(DefaultItemExcludes);$(DefaultExcludesInProjectFolder);$(DefaultWebContentItemExcludes)" Condition="'$(ExcludeConfigFilesFromBuildOutput)'=='true'" />
+    <Content Include="**\*.json" ExcludeFromSingleFile="true" CopyToPublishDirectory="PreserveNewest" Exclude="$(DefaultItemExcludes);$(DefaultExcludesInProjectFolder);$(DefaultWebContentItemExcludes)" Condition="'$(ExcludeConfigFilesFromBuildOutput)'=='true'" />
 
     <!-- Set CopyToPublishDirectory to Never for items under AppDesignerFolder ("Properties", by default) to avoid publishing launchSettings.json -->
     <Content Update="$(AppDesignerFolder)\**" CopyToPublishDirectory="Never" Condition="'$(AppDesignerFolder)' != ''"/>
diff --git a/src/Razor/Microsoft.NET.Sdk.Razor/src/build/netstandard2.0/Microsoft.NET.Sdk.Razor.DesignTime.targets b/src/Razor/Microsoft.NET.Sdk.Razor/src/build/netstandard2.0/Microsoft.NET.Sdk.Razor.DesignTime.targets
index 0b27cfce4a..4d8e0b5c4d 100644
--- a/src/Razor/Microsoft.NET.Sdk.Razor/src/build/netstandard2.0/Microsoft.NET.Sdk.Razor.DesignTime.targets
+++ b/src/Razor/Microsoft.NET.Sdk.Razor/src/build/netstandard2.0/Microsoft.NET.Sdk.Razor.DesignTime.targets
@@ -47,6 +47,17 @@ Copyright (c) .NET Foundation. All rights reserved.
     <ProjectCapability Include="SupportsTypeScriptNuGet" />
   </ItemGroup>
 
+  <!--
+    In order to properly support Blazor partial classes we need to ensure that older SDKs don't
+    add declaration files to the compile list. We do all the compilation work in-memory in latest
+    VS.
+  -->
+  <Target Name="_RemoveRazorDeclartionsFromCompile" AfterTargets="RazorGenerateComponentDeclaration">
+    <ItemGroup Condition="'$(DesignTimeBuild)'=='true'">
+      <Compile Remove="@(_RazorComponentDeclaration)" />
+    </ItemGroup>
+  </Target>
+
   <!--
     WebSdk imports these capabilities for nesting in DotNetCoreWeb projects.
     Conditinally import these capabilities if the project isn't targeting the WebSdk.
diff --git a/src/Razor/Microsoft.NET.Sdk.Razor/test/IntegrationTests/BuildIntrospectionTest.cs b/src/Razor/Microsoft.NET.Sdk.Razor/test/IntegrationTests/BuildIntrospectionTest.cs
index 2c86bf957c..fcb33acbf2 100644
--- a/src/Razor/Microsoft.NET.Sdk.Razor/test/IntegrationTests/BuildIntrospectionTest.cs
+++ b/src/Razor/Microsoft.NET.Sdk.Razor/test/IntegrationTests/BuildIntrospectionTest.cs
@@ -207,5 +207,19 @@ namespace Microsoft.AspNetCore.Razor.Design.IntegrationTests
             Assert.BuildOutputContainsLine(result, "Content: appsettings.json CopyToOutputDirectory=PreserveNewest CopyToPublishDirectory=PreserveNewest ExcludeFromSingleFile=true");
             Assert.BuildOutputContainsLine(result, "Content: appsettings.Development.json CopyToOutputDirectory=PreserveNewest CopyToPublishDirectory=PreserveNewest ExcludeFromSingleFile=true");
         }
+
+        [Fact]
+        [InitializeTestProject("SimpleMvc")]
+        public async Task IntrospectJsonContentFiles_WithExcludeConfigFilesFromBuildOutputSet()
+        {
+            // Verifies that the fix for https://github.com/aspnet/AspNetCore/issues/14017 works.
+            var result = await DotnetMSBuild("_IntrospectContentItems", "/p:ExcludeConfigFilesFromBuildOutput=true");
+
+            Assert.BuildPassed(result);
+            var launchSettingsPath = Path.Combine("Properties", "launchSettings.json");
+            Assert.BuildOutputContainsLine(result, $"Content: {launchSettingsPath} CopyToOutputDirectory= CopyToPublishDirectory=Never ExcludeFromSingleFile=true");
+            Assert.BuildOutputContainsLine(result, "Content: appsettings.json CopyToOutputDirectory= CopyToPublishDirectory=PreserveNewest ExcludeFromSingleFile=true");
+            Assert.BuildOutputContainsLine(result, "Content: appsettings.Development.json CopyToOutputDirectory= CopyToPublishDirectory=PreserveNewest ExcludeFromSingleFile=true");
+        }
     }
 }