Generic extension method to see if an enum contains a flag

Question

Considering this:

[Flags]
public enum MyEnum {
    One = 1,
    Two = 2,
    Four = 4,
    Eight = 8
}

public static class FlagsHelper
{
    public static bool          


        

Answer 1

You can basically use your existing extension method, byt use the Enum type instead of MyEnum. The problem then is that it doesn't know the enums are flags and won't allow the & operator, so you just have to convert the enum values to numbers.

    public static bool Contains(this Enum keys, Enum flag)
    {
        if (keys.GetType() != flag.GetType())
            throw new ArgumentException("Type Mismatch");
        return (Convert.ToUInt64(keys) & Convert.ToUInt64(flag)) != 0;
    }

And a unit test for good measure:

    [TestMethod]
    public void TestContains()
    {
        var e1 = MyEnum.One | MyEnum.Two;
        Assert.IsTrue( e1.Contains(MyEnum.Two) );

        var e2 = MyEnum.One | MyEnum.Four;
        Assert.IsFalse(e2.Contains(MyEnum.Two));
    }