Should I prefer the "is" or "how" operator?

Question

Possible duplicate:
casting vs using the keyword 'as' in the common language runtime

foreach (MyClass i in x) { if (i is IMy) { IMy a = (IMy)i; a.M1(); } } 

or

 foreach (MyClass i in x) { IMy a = i as IMy; if (a != null) { a.M1(); } } 

Answer 1

The second is preferable when you throw 1 time

Answer 2

I prefer the third option:

 foreach(var i in x.OfType<IMy>()) { i.M1(); } 

Answer 3

The second, since only one does it. Or you can use OfType method:

 foreach (IMy i in x.OfType<IMy>()) { i.M1(); } 

Answer 4

Secondly, it is preferable since you throw only once.

This article may also help to understand this. The operation "how" checks "is" and returns either a cast object or zero - it does all the work for you.

Answer 5

Second. The same number of lines of code, but you avoid throwing twice.

Note that while the second is preferable, it would not work, the type was the value type. You can use either for reference or null types.