Question

I have a generic class that takes a type T. Within this class I have a method were I need to compare a type T to another type T such as:

public class MyClass<T>
{
    public T MaxValue
    {
        // Implimentation for MaxValue
    }

    public T MyMethod(T argument)
    {
        if(argument > this.MaxValue)
        {
             // Then do something
        }
    }
}

The comparison operation inside of MyMethod fails with Compiler Error CS0019. Is it possible to add a constraint to T to make this work? I tried adding a where T: IComparable<T> to the class definition to no avail.

Answer 1

Adding constraint to make sure that the type implements IComparable<T> is a way to go. However, you cannot use the < operator – the interface provides a method CompareTo to do the same thing:

public class MyClass<T> where T : IComparable<T> { 
    public T MaxValue  { 
        // Implimentation for MaxValue 
    } 

    public T MyMethod(T argument) { 
        if(argument.CompareTo(this.MaxValue) > 0){ 
             // Then do something 
        } 
    } 
}

If you needed other numeric operators than just comparison, the situation is more difficult, because you cannot add constraint to support for example + operator and there is no corresponding interface. Some ideas about this can be found here.