How do I overload an operator for an enumeration in C#?

Question

I have an enumerated type that I would like to define the >, <, >=, and <= operators for. I know that these operators are implictly created on the basis of the enumerated type (as per the documentation) but I would like to explictly define these operators (for clarity, for control, to know how to do it, etc...)

I was hoping I could do something like:

public enum SizeType
{
    Small = 0,
    Medium = 1,
    Large = 2,
    ExtraLarge = 3
}

public SizeType operator >(SizeType x, SizeType y)
{

}

But this doesn't seem to work ("unexpected toke") ... is this possible? It seems like it should be since there are implictly defined operators. Any suggestions?

Answer 1

You can't do that. You can only provide overloaded operators for classes and structs you define -- and at least one of the parameters should be of type of the class or struct itself. That is, you can declare an overloaded addition operator that adds a MyClass to MyEnum but you can never do that with two MyEnum values.

Answer 2

As Mehrdad says, you can't do that on the enum itself. You could however make a couple of extension methods that work on your enum. That will make it look like methods on the enum.

static bool IsLessThan(this SizeType first, SizeType second) {
}

Answer 3

As other mentioned before, one cannot override operators on Enums, but you can do it on struct. See an example below. Let me know if it helped:

public struct SizeType
{
    private int InternalValue { get; set; }

    public static readonly int Small = 0;
    public static readonly int Medium = 1;
    public static readonly int Large = 2;
    public static readonly int ExtraLarge = 3;

    public override bool Equals(object obj)
    {
        SizeType otherObj = (SizeType)obj;
        return otherObj.InternalValue.Equals(this.InternalValue);
    }

    public static bool operator >(SizeType left, SizeType right)
    {
        return (left.InternalValue > right.InternalValue);
    }

    public static implicit operator SizeType(int otherType)
    {
        return new SizeType
        {
            InternalValue = otherType
        };
    }
}

public class test11
{
    void myTest()
    {
        SizeType smallSize = SizeType.Small;
        SizeType largeType = SizeType.Large;
        if (smallSize > largeType)
        {
            Console.WriteLine("small is greater than large");
        }
    }
}