[Blazor] Add support for RazorLangVersion 7.0 (#24383)

Author: javiercn

src/RazorSdk/SourceGenerators/Diagnostics/RazorSourceGeneratorResources.resx

@@ -121,7 +121,7 @@
     <value>Invalid RazorLangVersion</value>
   </data>
   <data name="InvalidRazorLangMessage" xml:space="preserve">
-    <value>Invalid value '{0}'' for RazorLangVersion. Valid values include 'Latest' or a valid version in range 1.0 to 5.0.</value>
+    <value>Invalid value '{0}'' for RazorLangVersion. Valid values include 'Latest' or a valid version in range 1.0 to 7.0.</value>
   </data>
   <data name="RecomputingTagHelpersTitle" xml:space="preserve">
     <value>Recomputing tag helpers</value>

src/RazorSdk/Targets/Sdk.Razor.CurrentVersion.targets

@@ -44,6 +44,16 @@ Copyright (c) .NET Foundation. All rights reserved.
 
   <!-- Resolve the TFM-specific attributes conditionally. -->
   <Choose>
+      <When Condition=" '$(TargetFrameworkIdentifier)' == '.NETCoreApp' AND $([MSBuild]::VersionGreaterThanOrEquals('$(TargetFrameworkVersion)', '7.0')) ">
+      <PropertyGroup>
+        <_TargetingNETCoreApp30OrLater>true</_TargetingNETCoreApp30OrLater>
+        <_TargetingNET50OrLater>true</_TargetingNET50OrLater>
+        <_TargetingNET60OrLater>true</_TargetingNET60OrLater>
+        <_TargetingNET70OrLater>true</_TargetingNET70OrLater>
+        <UseRazorSourceGenerator Condition="'$(Language)' == 'C#' AND '$(UseRazorSourceGenerator)' == '' ">true</UseRazorSourceGenerator>
+        <RazorLangVersion Condition="'$(RazorLangVersion)' == '' ">7.0</RazorLangVersion>
+      </PropertyGroup>
+    </When>
     <When Condition=" '$(TargetFrameworkIdentifier)' == '.NETCoreApp' AND $([MSBuild]::VersionGreaterThanOrEquals('$(TargetFrameworkVersion)', '6.0')) ">
       <PropertyGroup>
         <_TargetingNETCoreApp30OrLater>true</_TargetingNETCoreApp30OrLater>