Interlocked.CompareExchange with enum

Question

I\'m trying to use Interlocked.CompareExchange with this enum:

public enum State {
    Idle,
    Running,
    //...
}

The following code do

Answer 1

Using System.Runtime.CompilerServices.Unsafe

Here's a pretty good related answer going into depth.

using System;
using System.Runtime.CompilerServices;
using System.Threading;

public static class InterlockedEx
{
    /// 

    /// Enum equivalent of  and 
    /// 
    public static TEnum CompareExchange(ref TEnum location, TEnum value, TEnum comparand)
        where TEnum : struct, Enum
    {
        return Unsafe.SizeOf() switch
        {
            // .NET does not support 1- and 2-byte atomic operations as there
            // is no common hardware support for that.
            4 => CompareExchange32Bit(ref location, value, comparand),
            8 => CompareExchange64Bit(ref location, value, comparand),
            _ => throw new NotSupportedException("Only enums with an underlying type of 4 bytes or 8 bytes are allowed to be used with Interlocked")
        };

        static TEnum CompareExchange32Bit(ref TEnum location, TEnum value, TEnum comparand)
        {
            int comparandRaw = Unsafe.As(ref comparand);
            int valueRaw = Unsafe.As(ref value);
            ref int locationRaw = ref Unsafe.As(ref location);
            int returnRaw = Interlocked.CompareExchange(ref locationRaw, valueRaw, comparandRaw);
            return Unsafe.As(ref returnRaw);
        }

        static TEnum CompareExchange64Bit(ref TEnum location, TEnum value, TEnum comparand)
        {
            long comparandRaw = Unsafe.As(ref comparand);
            long valueRaw = Unsafe.As(ref value);
            ref long locationRaw = ref Unsafe.As(ref location);
            long returnRaw = Interlocked.CompareExchange(ref locationRaw, valueRaw, comparandRaw);
            return Unsafe.As(ref returnRaw);
        }
    }
}