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 [VariantEnum](https://github.com/prozolic/VariantEnum)
 ===
+
+[![MIT License](https://img.shields.io/github/license/prozolic/Utf8StringSplitter)](LICENSE)
+
+`VariantEnum` is C# Source Generator that automatically creates a Rust Enum-like `record class` from an `Enum`, where each variant can have a value.  
+The automatically created `record` class makes use of .NET 8 and C# 12 language features (`Incremental Generator`, `ISpanParsable<T>`, static abstract interfaces and Collection expressions).  
+This library is distributed via NuGet.
+
+> PM> Install-Package [VariantEnum](https://www.nuget.org/packages/VariantEnum/)
+
+
+How to use
+---
+
+If the `Enum` definition name ends with 'Variant', a record class is automatically created with the same name as the enum definition name without 'Variant'. 
+Enum members can be assigned the `[TVariantValueType]` attribute so that they have their own specific data.. Values can be accessed as argsXXX.  
+For example, if an `IpAddrVariant` Enum is defined:
+
+```csharp
+public enum IpAddrVariant : byte
+{
+    [VariantValueType(typeof(byte), typeof(byte), typeof(byte), typeof(byte))]
+    V4,
+    [VariantValueType(typeof(string))]
+    V6,
+    None
+}
+```
+
+This creates `IpAddr` record class.
+
+```csharp
+var ip = new IpAddr.V4(127, 0, 0, 1);
+
+var value = (IpAddr)ip switch
+{
+    IpAddr.V4 v4 => $"{v4.args0}.{v4.args1}.{v4.args2}.{v4.args3}",
+    IpAddr.V6 v6 => v6.args0,
+    _ => throw new Exception(),
+};
+
+Console.WriteLine(value); // 127.0.0.1
+```
+
+`IpAddr` record class automatically generates the following APIs.
+
+```csharp
+public abstract record IpAddr : ISpanFormattable, ISpanParsable<IpAddr>
+{
+    public sealed record V4(byte args0, byte args1, byte args2, byte args3) : IpAddr
+    {
+        public static V4 Default => new V4(args0: default, args1: default, args2: default, args3: default);
+        public override bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider? provider = null);
+    }
+
+    public sealed record V6(string args0) : IpAddr
+    {
+        public static V6 Default => new V6(args0: default);
+        public override bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider? provider = null);
+    }
+
+    public sealed record None : IpAddr
+    {
+        public static None Default => new None();
+        public override bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider? provider = null);
+    }
+
+    // ISpanFormattable
+    public abstract bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider? provider = null);
+    public string ToString(string? format, IFormatProvider? formatProvider) => ToString();
+
+    // ISpanParsable<T>
+    public static IpAddr Parse(ReadOnlySpan<char> s, IFormatProvider? provider = default);
+    public static bool TryParse(ReadOnlySpan<char> s, IFormatProvider? provider, [MaybeNullWhen(false)] out IpAddr result);
+
+    // IParsable<T>
+    public static IpAddr Parse(string s, IFormatProvider? provider = default);
+    public static bool TryParse([NotNullWhen(true)] string? s, IFormatProvider? provider, [MaybeNullWhen(false)] out IpAddr result);
+
+    public static int Count { get; } => 3;
+    public static string? GetName(IpAddr t); 
+    public static string[] GetNames() => [nameof(V4), nameof(V6), nameof(None)];
+    public static byte GetNumericValue(IpAddr t);
+    public static IpAddrVariant ConvertEnum(IpAddr t);
+    public static bool TryConvertEnum([NotNullWhen(true)] IpAddr? t, [MaybeNullWhen(false)] out IpAddrVariant result);
+    public static IpAddr Parse(ReadOnlySpan<char> s, bool ignoreCase, IFormatProvider? provider = default);
+    public static bool TryParse(ReadOnlySpan<char> s, out IpAddr result);
+    public static bool TryParse(ReadOnlySpan<char> s, bool ignoreCase, IFormatProvider? provider, [MaybeNullWhen(false)] out IpAddr result);
+    public static bool IsDefined(ReadOnlySpan<char> s);
+    public static bool IsDefined([NotNullWhen(true)] IpAddr? value);
+}
+```
+
+<details><summary>Generated All Code(IpAddr.g.cs)</summary>
+
+```csharp
+
+// <auto-generated> This .cs file is generated by VariantEnum. </auto-generated>
+#nullable enable
+#pragma warning disable CS0219 // The variable 'variable' is assigned but its value is never used
+#pragma warning disable CS8600 // Converting null literal or possible null value to non-nullable type.
+#pragma warning disable CS8601 // Possible null reference assignment.
+#pragma warning disable CS8602 // Dereference of a possibly null reference.
+#pragma warning disable CS8603 // Possible null reference return.
+#pragma warning disable CS8604 // Possible null reference argument for parameter.
+#pragma warning disable CS8619 // Possible null reference assignment fix
+
+using System;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using System.Runtime.CompilerServices;
+
+namespace ConsoleApp;
+
+public abstract record IpAddr : 
+    ISpanFormattable, 
+    ISpanParsable<IpAddr>
+{
+    public sealed record V4(byte args0, byte args1, byte args2, byte args3) : IpAddr
+    {
+        public static V4 Default => new V4(args0: default, args1: default, args2: default, args3: default);
+
+        public override bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider? provider = null)
+        {
+            var index = 0;
+            charsWritten = 0;
+
+            if (destination.Length < 5)
+            {
+                charsWritten += index;
+                return false;
+            }
+            destination[index++] = 'V';
+            destination[index++] = '4';
+            destination[index++] = ' ';
+            destination[index++] = '{';
+            destination[index++] = ' ';
+            var handler = new DefaultInterpolatedStringHandler();
+            handler.AppendLiteral("args0 = ");
+            handler.AppendFormatted(args0);
+            handler.AppendFormatted(", " );
+            handler.AppendLiteral("args1 = ");
+            handler.AppendFormatted(args1);
+            handler.AppendFormatted(", " );
+            handler.AppendLiteral("args2 = ");
+            handler.AppendFormatted(args2);
+            handler.AppendFormatted(", " );
+            handler.AppendLiteral("args3 = ");
+            handler.AppendFormatted(args3);
+            var print = handler.ToStringAndClear();
+            var printSpan = print.AsSpan();
+
+            if (destination.Length < printSpan.Length + index)
+            {
+                charsWritten += index;
+                return false;
+            }
+            printSpan.CopyTo(destination.Slice(index, printSpan.Length));
+            index += printSpan.Length;
+            if (destination.Length < 2 + index)
+            {
+                charsWritten += index;
+                return false;
+            }
+            destination[index++] = ' ';
+            destination[index++] = '}';
+
+            charsWritten = index;
+            return true;
+        }
+
+    }
+
+    public sealed record V6(string args0) : IpAddr
+    {
+        public static V6 Default => new V6(args0: default);
+
+        public override bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider? provider = null)
+        {
+            var index = 0;
+            charsWritten = 0;
+
+            if (destination.Length < 5)
+            {
+                charsWritten += index;
+                return false;
+            }
+            destination[index++] = 'V';
+            destination[index++] = '6';
+            destination[index++] = ' ';
+            destination[index++] = '{';
+            destination[index++] = ' ';
+            var handler = new DefaultInterpolatedStringHandler();
+            handler.AppendLiteral("args0 = ");
+            handler.AppendFormatted(args0);
+            var print = handler.ToStringAndClear();
+            var printSpan = print.AsSpan();
+
+            if (destination.Length < printSpan.Length + index)
+            {
+                charsWritten += index;
+                return false;
+            }
+            printSpan.CopyTo(destination.Slice(index, printSpan.Length));
+            index += printSpan.Length;
+            if (destination.Length < 2 + index)
+            {
+                charsWritten += index;
+                return false;
+            }
+            destination[index++] = ' ';
+            destination[index++] = '}';
+
+            charsWritten = index;
+            return true;
+        }
+
+    }
+
+    public sealed record None : IpAddr
+    {
+        public static None Default => new None();
+
+        public override bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider? provider = null)
+        {
+            var index = 0;
+            charsWritten = 0;
+
+            if (destination.Length < 8)
+            {
+                charsWritten += index;
+                return false;
+            }
+            destination[index++] = 'N';
+            destination[index++] = 'o';
+            destination[index++] = 'n';
+            destination[index++] = 'e';
+            destination[index++] = ' ';
+            destination[index++] = '{';
+            destination[index++] = ' ';
+            destination[index++] = '}';
+
+            charsWritten = index;
+            return true;
+        }
+
+    }
+
+
+    public abstract bool TryFormat(Span<char> destination, out int charsWritten, ReadOnlySpan<char> format = default, IFormatProvider? provider = null);
+
+    public string ToString(string? format, IFormatProvider? formatProvider) => ToString();
+
+    public static int Count => 3;
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static string? GetName(IpAddr ipaddr)
+    {
+        return ipaddr switch
+        {
+            V4 => nameof(V4),
+            V6 => nameof(V6),
+            None => nameof(None),
+            _ => null
+        };
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static string[] GetNames() => [nameof(V4), nameof(V6), nameof(None)];
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static byte GetNumericValue(IpAddr ipaddr)
+    {
+        return ipaddr switch
+        {
+            V4 => (byte)IpAddrVariant.V4,
+            V6 => (byte)IpAddrVariant.V6,
+            None => (byte)IpAddrVariant.None,
+            _ => ThrowInvalidType<byte>()
+        };
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static IpAddrVariant ConvertEnum(IpAddr ipaddr)
+    {
+        return ipaddr switch
+        {
+            V4 => IpAddrVariant.V4,
+            V6 => IpAddrVariant.V6,
+            None => IpAddrVariant.None,
+            _ => ThrowInvalidType<IpAddrVariant>()
+        };
+    }
+
+    public static bool TryConvertEnum([NotNullWhen(true)] IpAddr? ipaddr, [MaybeNullWhen(false)] out IpAddrVariant result)
+    {
+        switch(ipaddr)
+        {
+            case V4:
+                result = IpAddrVariant.V4;
+                return true;
+            case V6:
+                result = IpAddrVariant.V6;
+                return true;
+            case None:
+                result = IpAddrVariant.None;
+                return true;
+        }
+        result = default;
+        return false;
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static IpAddr Parse(string s, IFormatProvider? provider = default)
+    {
+        return Parse(s.AsSpan(), false, provider);
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static IpAddr Parse(ReadOnlySpan<char> s, IFormatProvider? provider = default)
+    {
+        return Parse(s, false, provider);
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static IpAddr Parse(ReadOnlySpan<char> s, bool ignoreCase, IFormatProvider? provider = default)
+    {
+        if (TryParse(s, ignoreCase, provider, out var result))
+        {
+            return result;
+        }
+        else
+        {
+            ThrowRequestedValueNotFound(s);
+            return default!;
+        }
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static bool TryParse([NotNullWhen(true)] string? s, IFormatProvider? provider, [MaybeNullWhen(false)] out IpAddr result)
+    {
+        return TryParse(s.AsSpan(), false, provider, out result);
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static bool TryParse(ReadOnlySpan<char> s, out IpAddr result)
+    {
+        return TryParse(s, false, null, out result);
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static bool TryParse(ReadOnlySpan<char> s, IFormatProvider? provider, [MaybeNullWhen(false)] out IpAddr result)
+    {
+        return TryParse(s, false, null, out result);
+    }
+
+    public static bool TryParse(ReadOnlySpan<char> s, bool ignoreCase, IFormatProvider? provider, [MaybeNullWhen(false)] out IpAddr result)
+    {
+        if (ignoreCase)
+        {
+            if (s.Equals(nameof(V4), StringComparison.OrdinalIgnoreCase))
+            {
+                result = V4.Default;
+                return true;
+            }
+            if (s.Equals(nameof(V6), StringComparison.OrdinalIgnoreCase))
+            {
+                result = V6.Default;
+                return true;
+            }
+            if (s.Equals(nameof(None), StringComparison.OrdinalIgnoreCase))
+            {
+                result = None.Default;
+                return true;
+            }
+
+            result = default;
+            return false;
+        }
+        else
+        {
+            switch (s)
+            {
+                case "V4":
+                    result = V4.Default;
+                    return true;
+                case "V6":
+                    result = V6.Default;
+                    return true;
+                case "None":
+                    result = None.Default;
+                    return true;
+            }
+            result = default;
+            return false;
+        }
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static bool IsDefined(ReadOnlySpan<char> s)
+    {
+        return s switch
+        {
+            "V4" => true,
+            "V6" => true,
+            "None" => true,
+            _ => false
+        };
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static bool IsDefined([NotNullWhen(true)] IpAddr? value)
+    {
+        return value switch
+        {
+            V4 => true,
+            V6 => true,
+            None => true,
+            _ => false
+        };
+    }
+
+    [DoesNotReturn]
+    private static void ThrowRequestedValueNotFound(ReadOnlySpan<char> s)
+    {
+        throw new ArgumentException($"Requested value '{s}' was not found.");
+    }
+
+    [DoesNotReturn]
+    private static T ThrowInvalidType<T>()
+    {
+        throw new ArgumentException($"Requested value was invalid type.'");
+    }
+}
+```
+
+</details>
+
+Auto-generated API
+---
+
+### Parse TryParse
+
+```csharp
+var v4 = IpAddr.Parse("V4");
+var v4IgnoreCase = IpAddr.Parse("v4", true);
+```
+
+```csharp
+if (IpAddr.TryParse("V4", out var v4))
+{
+    Console.WriteLine(v4); // V4 { args0 = 0, args1 = 0, args2 = 0, args3 = 0 }
+}
+
+if (IpAddr.TryParse("v4", true, null, out var v4IgnoreCase))
+{
+    Console.WriteLine(v4IgnoreCase); // V4 { args0 = 0, args1 = 0, args2 = 0, args3 = 0 }
+}
+```
+
+### Count
+
+```csharp
+var count = IpAddr.Count;
+Console.WriteLine(count); // 3
+```
+
+### GetName
+
+```csharp
+var name = IpAddr.GetName(new IpAddr.V4(127, 0, 0, 1));
+Console.WriteLine(name); // V4
+```
+
+### GetNames
+
+```csharp
+var names = IpAddr.GetNames();
+foreach (var name in names)
+{
+    Console.WriteLine(name);
+}
+// V4
+// V6
+// None
+```
+
+### IsDefined
+
+```csharp
+var result = IpAddr.IsDefined("V4");                            // true
+var result2 = IpAddr.IsDefined(new IpAddr.V4(127, 0, 0, 1));    // true
+```
+
+### GetNumericValue
+
+```csharp
+var v4Number = IpAddr.GetNumericValue(new IpAddr.V4(127, 0, 0, 1)); // 0
+var v6Number = IpAddr.GetNumericValue(new IpAddr.V6("::1"));        // 1
+```
+
+### ConvertEnum TryConvertEnum
+
+Get the enumeration value of the original enum from the specified member.
+
+```csharp
+IpAddrVariant variantEnum = IpAddr.ConvertEnum(new IpAddr.V4(127, 0, 0, 1));
+    
+if (IpAddr.TryConvertEnum(new IpAddr.V4(127, 0, 0, 1), out IpAddrVariant result))
+{
+}
+```
+
+License
+---
+
+MIT License.