Hello,

I am trying to understand the the XNA gamestate sample. Everything looks good except for one strange C# syntax that I have not seen before. It has to do with the ? operator. I am familiar with the conditional ? operator which can be used like this

(condition) ? statement if true : statement if false;

The code in the sample is

public PlayerIndex? ControllingPlayer
        {
            get { return controllingPlayer; }
            internal set { controllingPlayer = value; }
        }

        PlayerIndex? controllingPlayer;

where the PlayerIndex is an enum. The rest of the code also uses the PlayerIndex with a "?" at the end. What does the "?" operator do in this case?

Thanks. In the code they do assign a null value to this variable, and I was wondering how they did that since the values allowed by the PlayerIndex are One, Two, Three, and Four. The link that you provided was very useful, much appreciated.