Why do I get a set of numbers when I call GetType Name in MVC?

I'm using c# Asp.net MVC. I have a TPH model, so I am calling GetType().Name to find out which class type is being used. But sometimes when I call GetType().Name I not only get the name of the model but a large string of numbers after it. Why is this happening how can I avoid this?

example

public string DiscriminatorValue
{
    get{ return this.GetType.Name;
}
//...
RedirectToAction("Index", 
                 "Files", 
                  new { itemId = vm.itemid, 
                        itemtype = vm.item.DiscriminatorValue.ToString()});

and get this:

DiscriminatorActualValue_D808C81C7BDE227500B30C6760AC934EA4A1307BD88500694065B3389D2642B1