Cast Int to Generic Enum in C#

The simplest way I have found is to force the compiler's hand by adding a cast to object.

return (T)(object)i.Value;

You should be able to use Enum.Parse for this:

return (T)Enum.Parse(typeof(T), i.Value.ToString(), true);

This article talks about parsing generic enums for extenstion methods:

• Generic Enum Parsing with Extension Methods

Here's a very fast solution that abuses the fact that the runtime creates multiple instances of static generic classes. Unleash your inner optimization demons!

This really shines when you're reading Enums from a stream in a generic fashion. Combine with an outer class that also caches the enum's underlying type and a BitConverter to unleash the awesome.

void Main() 
{
    Console.WriteLine("Cast (reference): {0}", (TestEnum)5);
    Console.WriteLine("EnumConverter: {0}", EnumConverter<TestEnum>.Convert(5));
    Console.WriteLine("Enum.ToObject: {0}", Enum.ToObject(typeof(TestEnum), 5));

    int iterations = 1000 * 1000 * 100;
    Measure(iterations, "Cast (reference)", () => { var t = (TestEnum)5; });
    Measure(iterations, "EnumConverter", () => EnumConverter<TestEnum>.Convert(5));
    Measure(iterations, "Enum.ToObject", () => Enum.ToObject(typeof(TestEnum), 5));
}

static class EnumConverter<TEnum> where TEnum : struct, IConvertible
{
    public static readonly Func<long, TEnum> Convert = GenerateConverter();

    static Func<long, TEnum> GenerateConverter()
    {
        var parameter = Expression.Parameter(typeof(long));
        var dynamicMethod = Expression.Lambda<Func<long, TEnum>>(
            Expression.Convert(parameter, typeof(TEnum)),
            parameter);
        return dynamicMethod.Compile();
    }
}

enum TestEnum 
{
    Value = 5
}

static void Measure(int repetitions, string what, Action action)
{
    action();

    var total = Stopwatch.StartNew();
    for (int i = 0; i < repetitions; i++)
    {
        action();
    }
    Console.WriteLine("{0}: {1}", what, total.Elapsed);
}

Results on Core i7-3740QM with optimizations enabled:

Cast (reference): Value
EnumConverter: Value
Enum.ToObject: Value
Cast (reference): 00:00:00.3175615
EnumConverter: 00:00:00.4335949
Enum.ToObject: 00:00:14.3396366