Solve exception when building case insensitive lookup.

Author: electricessence

Source/EnumValue.cs

@@ -165,7 +165,18 @@ internal static Func<string, ValueLookupResult> ValueLookup
 	private static IReadOnlyDictionary<string, TEnum>? _ignoreCaseLookup;
 	internal static IReadOnlyDictionary<string, TEnum> IgnoreCaseLookup
 		=> LazyInitializer.EnsureInitialized(ref _ignoreCaseLookup,
-			() => Values.ToDictionary(e => Enum.GetName(typeof(TEnum), e)!, e => e, StringComparer.OrdinalIgnoreCase))!;
+			() =>
+			{
+				// If the enum has duplicate values, we want to use the first one.
+				var result = new Dictionary<string, TEnum>(StringComparer.OrdinalIgnoreCase);
+				foreach (var e in Values)
+				{
+					var v = Enum.GetName(typeof(TEnum), e);
+					if (result.ContainsKey(v)) continue;
+					result[v] = e;
+				}
+				return result;
+			})!;
 
 	static Entry[]?[] CreateLookup()
 	{

Source/Open.Text.csproj

@@ -19,7 +19,7 @@
 		<RepositoryUrl>https://github.com/Open-NET-Libraries/Open.Text</RepositoryUrl>
 		<RepositoryType>git</RepositoryType>
 		<PackageTags>string, span, enum, readonlyspan, text, format, split, trim, equals, trimmed equals, first, last, preceding, following, stringbuilder, extensions, stringcomparable, spancomparable, stringsegment, splitassegment</PackageTags>
-		<Version>6.6.3</Version>
+		<Version>6.6.4</Version>
 		<PackageReleaseNotes></PackageReleaseNotes>
 		<PackageLicenseExpression>MIT</PackageLicenseExpression>
 		<PublishRepositoryUrl>true</PublishRepositoryUrl>

Tests/EnumValueTests.cs

@@ -1,4 +1,5 @@
-using System;
+using FluentAssertions;
+using System;
 using System.Linq;
 using Xunit;
 
@@ -43,6 +44,15 @@ public enum Greek
 	None
 }
 
+public enum MultiCase
+{
+	Goodbye,
+	Hello,
+	HELLO,
+	hello,
+	goodbye
+}
+
 public enum LongEnum
 {
 	In_the_glowing_moonlight_the_winds_caress_and_serenade_the_silent_ocean_waves,
@@ -122,6 +132,19 @@ public enum LargeEnum
 
 public static class EnumValueTests
 {
+	[Fact]
+	public static void EnsureMultiCase()
+	{
+		EnumValue.TryParse<MultiCase>("HELLO", out var value).Should().Be(true);
+		value.Should().Be(MultiCase.HELLO);
+
+		EnumValue.TryParse("HELLO", true, out value).Should().Be(true);
+		value.Should().Be(MultiCase.Hello);
+
+		EnumValue.TryParse("goodbye", true, out value).Should().Be(true);
+		value.Should().Be(MultiCase.Goodbye);
+	}
+
 	[Fact]
 	public static void IsIntType()
 	{