Difference between generic argument constrained to an interface and just using the interface

Question

What is the difference between this:

void MyMethod(IMyInterface value)
{
    //...
}

and this:

void MyMethod(T val         


        

Answer 1

Jared has mentioned some of the points; another interesting one: with generics, you can avoid boxing of value-types as long as you basically don't touch it... so I could have a struct Foo : IMyInterface and pass it in, and it won't get boxed.

The difference gets more noticeable with things like collections:

static void Foo(IEnumerable data) {}

vs

static void Foo(IEnumerable data) 
    where T : IMyInterface {}

Now, since C# 3.0 doesn't have covariance (except for arrays), I can't pass a List to the top one, even if Bar : IMyInterface - but I can with the second (implicit T = Bar).