Question

Consider this admittedly contrived Generic Definition:

    private void Foo<T,BASETYPE>(PropertyInfo prop, BASETYPE o1, BASETYPE o2)
    {
        T value1 = (T) prop.GetValue(o1, null);
        T value2 = (T) prop.GetValue(o2, null);
        if (value1 != value2)
            Console.WriteLine("NOT EQUAL");
    }

prop is guaranteed to be a PropertyInfo for BASETYPE.

I am getting a compile error at the if() statement:

Operator '!=' cannot be applied to operands of type 'T' and 'T'

While in the “general case” I understand that the error message is valid, in this case, I only want the routine for some of the standard types: System.Int64, System.String, etc all of which support the == and != operator.

I assume this can be fixed with a “where” clause, but IComparable and IEqualable don’t help.

Do anyone know what the correct “where” clause is?

Frank

Answer 1

Since System.Int64, System.String, etc .. from your list implement IComparable, you could use

where T : IComparable

and use CompareTo() instead of !=

For eg. this code would compile

private void Foo<T>(object o) where T : IComparable
{
    T v1 = default(T);
    T v2 = default(T);
    if(v1.CompareTo(v2)  != 0)
    {
        Console.WriteLine("Not Equal");
    }
}

private void Bar()
{
    Foo<string>(new object());
}