Question

I just need to be able to cast an object to nullable enum. Object can be enum, null, or int. Thanks!

public enum MyEnum { A, B }
void Put(object value)
{
    System.Nullable<Myenum> val = (System.Nullable<MyEnum>)value;
}

Put(null);     // works
Put(Myenum.B); // works
Put(1);        // Invalid cast exception!!

Answer 1

How about:

MyEnum? val = value == null ? (MyEnum?) null : (MyEnum) value;

The cast from boxed int to MyEnum (if value is non-null) and then use the implicit conversion from MyEnum to Nullable<MyEnum>.

That’s okay, because you’re allowed to unbox from the boxed form of an enum to its underlying type, or vice versa.

I believe this is actually a conversion which isn’t guaranteed to work by the C# spec, but is guaranteed to work by the CLI spec. So as long as you’re running your C# code on a CLI implementation (which you will be 🙂 you’ll be fine.