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 t)   {     if (T is MyClass)     {         MyClass mc = (MyClass)t          ...     }     else if (T is List<MyClass>)     {         List<MyClass> lmc = (List<MyClass>)t         ...     } } 

Answer 1

Yes:

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