Question

Dummy code:

public object Addition(object a, object b)
{
    var type = a.GetType();
    var op = type.GetMethod("op_Addition", BindingFlags.Static | BindingFlags.Public);
    return op.Invoke(null, new object[] { a, b });
}

This method complains with int/float/double,that can’t find these methods(op_Addition).

So how to build a general addition method?

Answer 1

Yes, they’re not custom operators which exist as members like that – there are built-in IL instructions instead.

(The same is almost true for string concatenation, except there the C# compiler builds a call to string.Concat.)

If you’re using C# 4 and .NET 4, the simplest approach is to use dynamic typing:

public dynamic Addition(dynamic x, dynamic y)
{
    return x + y;
}

For earlier versions, you’ll need to special-case certain types 🙁

It’s not clear what your context is, but you may find Marc Gravell’s article on generic operators interesting.