Checking type parameter of a generic method in C#

Question

Is it possible to do something like this in C#:

public void DoSomething(T t)  
{
    if (T is MyClass)
    {
        MyClass mc = (MyClass)t 
               


        

Answer 1

Yes:

if (typeof(T) == typeof(MyClass))
{
    MyClass mc = (MyClass)(object) t;
}
else if (typeof(T) == typeof(List))
{
    List lmc = (List)(object) t;
}

It's slightly odd that you need to go via a cast to object, but that's just the way that generics work - there aren't as many conversions from a generic type as you might expect.

Of course another alternative is to use the normal execution time check:

MyClass mc = t as MyClass;
if (mc != null)
{
    // ...
}
else
{
    List lmc = t as List;
    if (lmc != null)
    {
        // ...
    }
}

That will behave differently to the first code block if t is null, of course.

I would try to avoid this kind of code where possible, however - it can be necessary sometimes, but the idea of generic methods is to be able to write generic code which works the same way for any type.