Used expression tree to GetName for enums.

Author: electricessence

Source/EnumValue.cs

@@ -40,11 +40,35 @@ public EnumValue(string value)
 		/// <summary>
 		/// Returns the string representation of the enum value.
 		/// </summary>
-		public override string ToString() => NameLookup[Value];
+		public override string ToString() => NameLookup(Value);
 
 		internal static readonly (string Name, TEnum Value)[]?[] Lookup = CreateLookup();
 
-		internal static readonly ImmutableSortedDictionary<TEnum, string> NameLookup = CreateNameLookup();
+		internal static readonly Func<TEnum, string> NameLookup = GetEnumNameDelegate();
+
+		static Func<TEnum, string> GetEnumNameDelegate()
+		{
+			var eValue = Expression.Parameter(typeof(TEnum), "value"); // (TEnum value)
+			var tEnum = typeof(TEnum);
+			var tResult = typeof(string);
+
+			return
+			  Expression.Lambda<Func<TEnum, string>>(
+				Expression.Block(tResult,
+				  Expression.Switch(tResult, eValue,
+					Expression.Block(tResult,
+					  Expression.Throw(Expression.New(typeof(Exception).GetConstructor(Type.EmptyTypes))),
+					  Expression.Default(tResult)
+					),
+					null,
+					Enum.GetValues(tEnum).Cast<Object>().Select(v => Expression.SwitchCase(
+					  Expression.Constant(v.ToString()),
+					  Expression.Constant(v)
+					)).ToArray()
+				  )
+				), eValue
+			  ).Compile();
+		}
 
 		static (string Name, TEnum Value)[]?[] CreateLookup()
 		{
@@ -267,6 +291,6 @@ public static bool TryParse<TEnum>(string value, bool ignoreCase, out TEnum e)
 		/// <param name="value">The enum value to get the name for.</param>
 		/// <returns>The name of the enum.</returns>
 		public static string GetName<TEnum>(TEnum value) where TEnum : Enum
-			=> EnumValue<TEnum>.NameLookup[value];
+			=> EnumValue<TEnum>.NameLookup(value);
 	}
 }

Source/Open.Text.csproj

@@ -17,7 +17,7 @@
 		<RepositoryUrl>https://github.com/Open-NET-Libraries/Open.Text</RepositoryUrl>
 		<RepositoryType>git</RepositoryType>
 		<PackageTags>dotnet, dotnetcore, string, span, readonlyspan, text, format, split, trim, equals, trimmed equals, first, last, preceding, following, stringbuilder, extensions</PackageTags>
-		<Version>3.4.0</Version>
+		<Version>3.4.1</Version>
 		<PackageReleaseNotes></PackageReleaseNotes>
 		<PackageLicenseExpression>MIT</PackageLicenseExpression>
 		<PublishRepositoryUrl>true</PublishRepositoryUrl>

Tests/EnumValueTests.cs

@@ -5,7 +5,7 @@ namespace Open.Text.Tests
 {
 	public static class EnumValueTests
 	{
-		enum Greek
+		public enum Greek
 		{
 			Alpha, Beta, Gamma
 		}
@@ -35,6 +35,18 @@ public static void EvalValueParseFail(string value)
 			Assert.False(EnumValue.TryParse<Greek>(value, true, out _));
 		}
 
+
+		[Theory]
+		[InlineData(Greek.Alpha)]
+		[InlineData(Greek.Beta)]
+		[InlineData(Greek.Gamma)]
+
+		public static void GetName(Greek expected)
+		{
+			var s = expected.ToString();
+			Assert.Equal(s, EnumValue.GetName(expected));
+		}
+
 		static void CheckImplicit(EnumValue<Greek> value, Greek expected)
 		{
 			Assert.Equal(expected, value);
@@ -54,5 +66,6 @@ static void CheckImplicitCaseIgnored(EnumValueCaseIgnored<Greek> value, Greek ex
 			Assert.False(value != expected);
 			Assert.False(value != new EnumValue<Greek>(expected));
 		}
+
 	}
 }