diff --git a/src/Microsoft.AspNetCore.Razor.Language/Properties/Resources.Designer.cs b/src/Microsoft.AspNetCore.Razor.Language/Properties/Resources.Designer.cs
index adb2a92453..1f95e0176c 100644
--- a/src/Microsoft.AspNetCore.Razor.Language/Properties/Resources.Designer.cs
+++ b/src/Microsoft.AspNetCore.Razor.Language/Properties/Resources.Designer.cs
@@ -822,6 +822,20 @@ namespace Microsoft.AspNetCore.Razor.Language
         internal static string FormatSectionDirective_NameToken_Name()
             => GetString("SectionDirective_NameToken_Name");
 
+        /// <summary>
+        /// The Razor language version '{0}' is unrecognized or not supported by this version of Razor.
+        /// </summary>
+        internal static string RazorLanguageVersion_InvalidVersion
+        {
+            get => GetString("RazorLanguageVersion_InvalidVersion");
+        }
+
+        /// <summary>
+        /// The Razor language version '{0}' is unrecognized or not supported by this version of Razor.
+        /// </summary>
+        internal static string FormatRazorLanguageVersion_InvalidVersion(object p0)
+            => string.Format(CultureInfo.CurrentCulture, GetString("RazorLanguageVersion_InvalidVersion"), p0);
+
         private static string GetString(string name, params string[] formatterNames)
         {
             var value = _resourceManager.GetString(name);
diff --git a/src/Microsoft.AspNetCore.Razor.Language/RazorConfiguration.cs b/src/Microsoft.AspNetCore.Razor.Language/RazorConfiguration.cs
index 32420721ee..0f00751497 100644
--- a/src/Microsoft.AspNetCore.Razor.Language/RazorConfiguration.cs
+++ b/src/Microsoft.AspNetCore.Razor.Language/RazorConfiguration.cs
@@ -2,25 +2,58 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Generic;
+using System.Linq;
 
 namespace Microsoft.AspNetCore.Razor.Language
 {
     public sealed class RazorConfiguration
     {
-        public static readonly RazorConfiguration DefaultRuntime = new RazorConfiguration(RazorLanguageVersion.Latest, designTime: false);
-        public static readonly RazorConfiguration DefaultDesignTime = new RazorConfiguration(RazorLanguageVersion.Latest, designTime: true);
+        public static readonly RazorConfiguration Default = new RazorConfiguration(
+            RazorLanguageVersion.Latest, 
+            "unnamed",
+            Array.Empty<RazorExtension>(),
+            designTime: false);
 
-        public RazorConfiguration(RazorLanguageVersion languageVersion, bool designTime)
+        // This is used only in some back-compat scenarios. We don't expose it because there's no
+        // use case for anyone else to use it.
+        internal static readonly RazorConfiguration DefaultDesignTime = new RazorConfiguration(
+            RazorLanguageVersion.Latest,
+            "unnamed",
+            Array.Empty<RazorExtension>(),
+            designTime: true);
+
+        public RazorConfiguration(
+            RazorLanguageVersion languageVersion, 
+            string configurationName,
+            IEnumerable<RazorExtension> extensions,
+            bool designTime)
         {
             if (languageVersion == null)
             {
                 throw new ArgumentNullException(nameof(languageVersion));
             }
 
+            if (configurationName == null)
+            {
+                throw new ArgumentNullException(nameof(configurationName));
+            }
+
+            if (extensions == null)
+            {
+                throw new ArgumentNullException(nameof(extensions));
+            }
+
             LanguageVersion = languageVersion;
+            ConfigurationName = configurationName;
+            Extensions = extensions.ToArray();
             DesignTime = designTime;
         }
 
+        public string ConfigurationName { get; }
+
+        public IReadOnlyList<RazorExtension> Extensions { get; }
+
         public RazorLanguageVersion LanguageVersion { get; }
 
         public bool DesignTime { get; }
diff --git a/src/Microsoft.AspNetCore.Razor.Language/RazorEngine.cs b/src/Microsoft.AspNetCore.Razor.Language/RazorEngine.cs
index 0fe5e14d19..aa06b9f9ab 100644
--- a/src/Microsoft.AspNetCore.Razor.Language/RazorEngine.cs
+++ b/src/Microsoft.AspNetCore.Razor.Language/RazorEngine.cs
@@ -15,7 +15,7 @@ namespace Microsoft.AspNetCore.Razor.Language
             return Create(configure: null);
         }
 
-        public static RazorEngine Create(Action<IRazorEngineBuilder> configure) => CreateCore(RazorConfiguration.DefaultRuntime, configure);
+        public static RazorEngine Create(Action<IRazorEngineBuilder> configure) => CreateCore(RazorConfiguration.Default, configure);
 
         public static RazorEngine CreateDesignTime()
         {
diff --git a/src/Microsoft.AspNetCore.Razor.Language/RazorExtension.cs b/src/Microsoft.AspNetCore.Razor.Language/RazorExtension.cs
new file mode 100644
index 0000000000..feb94b0ede
--- /dev/null
+++ b/src/Microsoft.AspNetCore.Razor.Language/RazorExtension.cs
@@ -0,0 +1,10 @@
+// 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.
+
+namespace Microsoft.AspNetCore.Razor.Language
+{
+    public abstract class RazorExtension
+    {
+        public abstract string ExtensionName { get; }
+    }
+}
diff --git a/src/Microsoft.AspNetCore.Razor.Language/RazorLanguageVersion.cs b/src/Microsoft.AspNetCore.Razor.Language/RazorLanguageVersion.cs
index 721c84ff00..c200290878 100644
--- a/src/Microsoft.AspNetCore.Razor.Language/RazorLanguageVersion.cs
+++ b/src/Microsoft.AspNetCore.Razor.Language/RazorLanguageVersion.cs
@@ -2,10 +2,12 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Diagnostics;
 
 namespace Microsoft.AspNetCore.Razor.Language
 {
-    public sealed class RazorLanguageVersion : IEquatable<RazorLanguageVersion>
+    [DebuggerDisplay("{" + nameof(DebuggerToString) + "(),nq}")]
+    public sealed class RazorLanguageVersion : IEquatable<RazorLanguageVersion>, IComparable<RazorLanguageVersion>
     {
         public static readonly RazorLanguageVersion Version_1_0 = new RazorLanguageVersion(1, 0);
 
@@ -17,6 +19,60 @@ namespace Microsoft.AspNetCore.Razor.Language
 
         public static readonly RazorLanguageVersion Latest = Version_2_1;
 
+        public static bool TryParse(string languageVersion, out RazorLanguageVersion version)
+        {
+            if (languageVersion == null)
+            {
+                throw new ArgumentNullException(nameof(languageVersion));
+            }
+
+            if (string.Equals(languageVersion, "latest", StringComparison.OrdinalIgnoreCase))
+            {
+                version = Version_2_1;
+                return true;
+            }
+            else if (languageVersion == "2.1")
+            {
+                version = Version_2_1;
+                return true; 
+            }
+            else if (languageVersion == "2.0")
+            {
+                version = Version_2_0;
+                return true;
+            }
+            else if (languageVersion == "1.1")
+            {
+                version = Version_1_1;
+                return true;
+            }
+            else if (languageVersion == "1.0")
+            {
+                version = Version_1_0;
+                return true;
+            }
+
+            version = null;
+            return false;
+        }
+
+        public static RazorLanguageVersion Parse(string languageVersion)
+        {
+            if (languageVersion == null)
+            {
+                throw new ArgumentNullException(nameof(languageVersion));
+            }
+
+            if (TryParse(languageVersion, out var parsed))
+            {
+                return parsed;
+            }
+
+            throw new ArgumentException(
+                Resources.FormatRazorLanguageVersion_InvalidVersion(languageVersion), 
+                nameof(languageVersion));
+        }
+
         // Don't want anyone else constructing language versions.
         private RazorLanguageVersion(int major, int minor)
         {
@@ -28,6 +84,22 @@ namespace Microsoft.AspNetCore.Razor.Language
 
         public int Minor { get; }
 
+        public int CompareTo(RazorLanguageVersion other)
+        {
+            if (other == null)
+            {
+                throw new ArgumentNullException(nameof(other));
+            }
+
+            var result = Major.CompareTo(other.Major);
+            if (result != 0)
+            {
+                return result;
+            }
+
+            return Minor.CompareTo(other.Minor);
+        }
+
         public bool Equals(RazorLanguageVersion other)
         {
             if (other == null)
@@ -44,7 +116,9 @@ namespace Microsoft.AspNetCore.Razor.Language
             // We don't need to do anything special for our hash code since reference equality is what we're going for.
             return base.GetHashCode();
         }
+        
+        public override string ToString() => $"{Major}.{Minor}";
 
-        public override string ToString() => $"Razor '{Major}.{Minor}'";
+        private string DebuggerToString() => $"Razor '{Major}.{Minor}'";
     }
 }
diff --git a/src/Microsoft.AspNetCore.Razor.Language/RazorParserFeatureFlags.cs b/src/Microsoft.AspNetCore.Razor.Language/RazorParserFeatureFlags.cs
index 19b1d54e80..0629eb9af8 100644
--- a/src/Microsoft.AspNetCore.Razor.Language/RazorParserFeatureFlags.cs
+++ b/src/Microsoft.AspNetCore.Razor.Language/RazorParserFeatureFlags.cs
@@ -9,8 +9,9 @@ namespace Microsoft.AspNetCore.Razor.Language
         {
             var allowMinimizedBooleanTagHelperAttributes = false;
 
-            if (version == RazorLanguageVersion.Version_2_1)
+            if (version.CompareTo(RazorLanguageVersion.Version_2_1) >= 0)
             {
+                // Added in 2.1
                 allowMinimizedBooleanTagHelperAttributes = true;
             }
 
diff --git a/src/Microsoft.AspNetCore.Razor.Language/Resources.resx b/src/Microsoft.AspNetCore.Razor.Language/Resources.resx
index 54df909c15..35b511066d 100644
--- a/src/Microsoft.AspNetCore.Razor.Language/Resources.resx
+++ b/src/Microsoft.AspNetCore.Razor.Language/Resources.resx
@@ -291,4 +291,7 @@
   <data name="SectionDirective_NameToken_Name" xml:space="preserve">
     <value>SectionName</value>
   </data>
+  <data name="RazorLanguageVersion_InvalidVersion" xml:space="preserve">
+    <value>The Razor language version '{0}' is unrecognized or not supported by this version of Razor.</value>
+  </data>
 </root>
\ No newline at end of file
diff --git a/src/Microsoft.AspNetCore.Razor.Runtime/Hosting/RazorConfigurationNameAttribute.cs b/src/Microsoft.AspNetCore.Razor.Runtime/Hosting/RazorConfigurationNameAttribute.cs
new file mode 100644
index 0000000000..034e64c309
--- /dev/null
+++ b/src/Microsoft.AspNetCore.Razor.Runtime/Hosting/RazorConfigurationNameAttribute.cs
@@ -0,0 +1,38 @@
+// 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.Hosting
+{
+    /// <summary>
+    /// Specifies the name of a Razor configuration as defined by the Razor SDK.
+    /// </summary>
+    /// <remarks>
+    /// This attribute is applied to an application's entry point assembly by the Razor SDK during the build, 
+    /// so that the Razor configuration can be loaded at runtime based on the settings provided by the project
+    /// file.
+    /// </remarks>
+    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = false, Inherited = false)]
+    public sealed class RazorConfigurationNameAttribute : Attribute
+    {
+        /// <summary>
+        /// Creates a new instance of <see cref="RazorConfigurationNameAttribute"/>.
+        /// </summary>
+        /// <param name="configurationName">The name of the Razor configuration.</param>
+        public RazorConfigurationNameAttribute(string configurationName)
+        {
+            if (configurationName == null)
+            {
+                throw new ArgumentNullException(nameof(configurationName));
+            }
+
+            ConfigurationName = configurationName;
+        }
+
+        /// <summary>
+        /// Gets the name of the Razor configuration.
+        /// </summary>
+        public string ConfigurationName { get; }
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.AspNetCore.Razor.Runtime/Hosting/RazorExtensionAssemblyNameAttribute.cs b/src/Microsoft.AspNetCore.Razor.Runtime/Hosting/RazorExtensionAssemblyNameAttribute.cs
new file mode 100644
index 0000000000..92a9d1c6ec
--- /dev/null
+++ b/src/Microsoft.AspNetCore.Razor.Runtime/Hosting/RazorExtensionAssemblyNameAttribute.cs
@@ -0,0 +1,50 @@
+// 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.Hosting
+{
+    /// <summary>
+    /// Specifies the name of a Razor extension as defined by the Razor SDK.
+    /// </summary>
+    /// <remarks>
+    /// This attribute is applied to an application's entry point assembly by the Razor SDK during the build, 
+    /// so that the Razor configuration can be loaded at runtime based on the settings provided by the project
+    /// file.
+    /// </remarks>
+    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = true, Inherited = false)]
+    public sealed class RazorExtensionAssemblyNameAttribute : Attribute
+    {
+        /// <summary>
+        /// Creates a new instance of <see cref="RazorExtensionAssemblyNameAttribute"/>.
+        /// </summary>
+        /// <param name="extensionName">The name of the extension.</param>
+        /// <param name="assemblyName">The assembly name of the extension.</param>
+        public RazorExtensionAssemblyNameAttribute(string extensionName, string assemblyName)
+        {
+            if (extensionName == null)
+            {
+                throw new ArgumentNullException(nameof(extensionName));
+            }
+
+            if (assemblyName == null)
+            {
+                throw new ArgumentNullException(nameof(assemblyName));
+            }
+
+            ExtensionName = extensionName;
+            AssemblyName = assemblyName;
+        }
+
+        /// <summary>
+        /// Gets the assembly name of the extension.
+        /// </summary>
+        public string AssemblyName { get; }
+
+        /// <summary>
+        /// Gets the name of the extension.
+        /// </summary>
+        public string ExtensionName { get; }
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.AspNetCore.Razor.Runtime/Hosting/RazorLanguageVersionAttribute.cs b/src/Microsoft.AspNetCore.Razor.Runtime/Hosting/RazorLanguageVersionAttribute.cs
new file mode 100644
index 0000000000..8f261143d0
--- /dev/null
+++ b/src/Microsoft.AspNetCore.Razor.Runtime/Hosting/RazorLanguageVersionAttribute.cs
@@ -0,0 +1,38 @@
+// 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.Hosting
+{
+    /// <summary>
+    /// Specifies the name of a Razor configuration as defined by the Razor SDK.
+    /// </summary>
+    /// <remarks>
+    /// This attribute is part of a set of metadata attributes that can be applied to an assembly at build
+    /// time by the Razor SDK. These attributes allow the Razor configuration to be loaded at runtime based 
+    /// on the settings originally provided by the project file.
+    /// </remarks>
+    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = false, Inherited = false)]
+    public sealed class RazorLanguageVersionAttribute : Attribute
+    {
+        /// <summary>
+        /// Creates a new instance of <see cref="RazorLanguageVersionAttribute"/>.
+        /// </summary>
+        /// <param name="languageVersion">The language version of Razor</param>
+        public RazorLanguageVersionAttribute(string languageVersion)
+        {
+            if (languageVersion == null)
+            {
+                throw new ArgumentNullException(nameof(languageVersion));
+            }
+
+            LanguageVersion = languageVersion;
+        }
+
+        /// <summary>
+        /// Gets the Razor language version.
+        /// </summary>
+        public string LanguageVersion { get; }
+    }
+}
\ No newline at end of file
diff --git a/src/Microsoft.VisualStudio.Editor.Razor/DefaultTemplateEngineFactoryService.cs b/src/Microsoft.VisualStudio.Editor.Razor/DefaultTemplateEngineFactoryService.cs
index a82d1b8e94..ab5518bb46 100644
--- a/src/Microsoft.VisualStudio.Editor.Razor/DefaultTemplateEngineFactoryService.cs
+++ b/src/Microsoft.VisualStudio.Editor.Razor/DefaultTemplateEngineFactoryService.cs
@@ -43,7 +43,7 @@ namespace Microsoft.VisualStudio.Editor.Razor
             var project = FindProject(projectPath);
             var configuration = (project?.Configuration as MvcExtensibilityConfiguration) ?? DefaultConfiguration;
             var razorLanguageVersion = configuration.LanguageVersion;
-            var razorConfiguration = new RazorConfiguration(razorLanguageVersion, designTime: true);
+            var razorConfiguration = new RazorConfiguration(razorLanguageVersion, "unnamed", Array.Empty<RazorExtension>(), designTime: true);
 
             RazorEngine engine;
             if (razorLanguageVersion.Major == 1)