Compare class type without instance

Question

I have a 'factory' class that should compare the generic class type parameter and return a specific instance of an object:

public static class MyExceptionFactory<T> where T: System.Exception {
    public static MyReturnObj Create() {
        // return instance of MyReturnObj based on type of T
    }
}

But I can't check if e.g. T is ArgumentNullException because T is a type parameter and not a variable

if(T is ArgumentNullException) // won't work

.. and also, I can't check for the type of T

if(typeof(T) is ArgumentNullException)

because IntelliSense tells me that T is never System.ArgumentNullException (I assume because T is System.Exception)

How could I solve this? Do I have to pass an instance of a System.Exception to check it's type or is there any other way to do it via class type parameter?

Answer 1

You have two type identifiers, you just need to compare the types.

if(typeof(T) == typeof(ArgumentNullException))
{
   ...
}

Answer 2

If inherited types should be respected, use:

if(typeof(ArgumentNullException).IsAssignableFrom(typeof(T)))
{
...
}

Answer 3

if (typeof(T) == typeof(ArgumentNullException))
{
    //your code
}