Update tests to allow .NET 10.0 (#7439)

* Update tests to allow .NET 10.0

* Add a way to handle preview for LangVersion

* Update ProjectLangVersion.cs

* Add the .NET 10.0-windows target

* Turn the dictionary to <int, string>

* Turn the dictionary into just a constant.

* Better name for the constant and pin it to 13

* Tweaks

---------

Co-authored-by: Brandon Ording <[email protected]>

Author: tamararivera

tests/IntegrityTests/ProjectFrameworks.cs

@@ -36,7 +36,7 @@ public void TargetFrameworkElementShouldAgreeWithFrameworkCount()
                 });
         }
 
-        public static readonly string[] sdkProjectAllowedTfmList = ["net9.0", "net9.0-windows", "net8.0", "net8.0-windows", "net48", "netstandard2.0"];
+        public static readonly string[] sdkProjectAllowedTfmList = ["net10.0", "net10.0-windows", "net9.0", "net9.0-windows", "net8.0", "net8.0-windows", "net48", "netstandard2.0"];
         static readonly string[] nonSdkProjectAllowedFrameworkList = ["v4.8"];
 
         [Test]

tests/IntegrityTests/ProjectLangVersion.cs

@@ -83,7 +83,8 @@ public void SamplesShouldUseCorrectLangVersion()
 
                     solutionLangVersion ??= fallbackLangVersion;
 
-                    var solutionLangVersionString = solutionLangVersion.Value.ToString("N1");
+                    var solutionLangVersionString = solutionLangVersion > latestReleasedLangVersion ? "preview" : solutionLangVersion.Value.ToString("N1");
+
                     bool valid = true;
 
                     foreach (var projectFile in projectFiles)
@@ -162,6 +163,11 @@ public void ShouldHaveLangVersionMappingForEachAllowedTargetFramework()
             { "net8.0-windows", 12 },
             { "net9.0", 13 },
             { "net9.0-windows", 13 },
+            { "net10.0", 14 },
+            { "net10.0-windows", 14 }
         };
+
+        // This needs to be kept up to date with the latest released version of C#
+        private const int latestReleasedLangVersion = 13;
     }
 }