Enum Boxing and Equality

Question

Why does this return False

    public enum Directions { Up, Down, Left, Right }

    static void Main(string[] args)
    {
        bool matches = IsOneOf(Directi         


        

Answer 1

Enum does not implement a == equality operator but it does override the Equals method.

Since it does not implement ==, the system performs a reference equality check. Note that System.Enum is a class not a structure. Hence, values such as Directions.Left are boxed. In this particular case, the boxed objects end up being separate objects, hence they fail a reference equality test.

The compiler understands == for concrete Enum types (such as Directions), but the compiler does not do this special processing against the System.Enum type.

Answer 2

As JB says, boxing. You can see this by changing from Enum to Directions:

public static bool IsOneOf(Directions self, params Directions[] values)
{
    foreach (var value in values)
        if (self == value)
            return true;
    return false;
}

true is returned.