Fix creating RegionInfo object using names with different casing.

src/libraries/System.Globalization/tests/System/Globalization/RegionInfoTests.cs

@@ -79,6 +79,24 @@ public void CurrentRegion_Windows()
  }).Dispose();
  }
 
+
+ [ConditionalTheory(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+ // We are testing with "no" as it match a neutral culture name. We want ensure this not conflict with region name.
+ [InlineData("no")]
+ [InlineData("No")]
+ [InlineData("NO")]
+ public void ValidateUsingCasedRegionName(string regionName)
+ {
+ RemoteExecutor.Invoke(name =>
+ {
+ // It is important to do this test in the following order because we have internal cache for regions.
+ // creating the region with the original input name should be the first to do to ensure not cached before.
+ string resultedName = new RegionInfo(name).Name;
+ string expectedName = new RegionInfo(name.ToUpperInvariant()).Name;
+ Assert.Equal(expectedName, resultedName);
+ }, regionName).Dispose();
+ }
+
  [Theory]
  [InlineData("en-US", "United States")]
  [OuterLoop("May fail on machines with multiple language packs installed")] // see https://github.com/dotnet/runtime/issues/30132

src/libraries/System.Private.CoreLib/src/System/Globalization/CultureData.cs

@@ -152,7 +152,7 @@ internal partial class CultureData
  /// </remarks>
  private static Dictionary<string, string> RegionNames =>
  s_regionNames ??=
- new Dictionary<string, string>(257 /* prime */)
+ new Dictionary<string, string>(257 /* prime */, StringComparer.OrdinalIgnoreCase)
  {
  { "001", "en-001" },
  { "029", "en-029" },