Typecasting in C#

[Zombimode]

For some reason typecasting doesn't seem to work like it does in other languages.

Maybe I'm just missing something.

Consider the following set-up:

public class BaseClass {

}

public class DerivativeClass : BaseClass {
   public void DoStuff(){
      //do stuff
   }
}

Now lets assume a method as our context that takes an object of BaseClass as parameter. Naturally the method accepts objects of DerivativeClass too. And if the object is of the DerivativeClass type, DoStuff shall be called. All in all a very simple set-up that can come up reasonably often. In all other programming languages I know the following would work:

public void CallingContext(BaseClass anObject){
   if (anObject is DerivativeClass){
      (DerivativeClass)anObject.DoStuff;
   }
}

But C# doesn't like that. Regardless of the cast I can only see what fields and methods are available in BaseClass.
Instead, C# forces the following construct:

public void CallingContext(BaseClass anObject){
   if (anObject is DerivativeClass){
      DerivativeClass dummy = (DerivativeClass)anObject;
      dummy.DoStuff;
   }
}

Why, C#, why?
This is incredibly clunky and makes the code look stupid.

Do I miss something or is C# (which I like otherwise) just dumb in this regard?

[Jasdoif]

If I'm reading this right, you should be able to do

((DerivativeClass)anObject).DoStuff

.

[Douglas]

What you're missing is the order of operations involved - the dot happens before the cast, so you're casting the result of "derivedObject.DoStuff" to the derived type. If you want to cast first, the line needs to be this:

((DerivativeClass)anObject).DoStuff;

But! If you're working with the latest version of C#, version 7 which comes with Visual Studio 2017, there's a much more convenient way to do it:

if (anObject is DerivativeClass derivedObject) {
    derivedObject.DoStuff;
}

Yes, that's a variable declaration and assignment inside that conditional, accomplished by nothing more than adding the new variable's name to the end of the type check. It's called Pattern Matching, and was specifically designed for exactly this use case.