[Resolved] Casting Reference Types

[wey97]

Consider:

Control c = new Control();
object o = (object)c;
Control x = (Control)o;

and:

Control c = new Control();
object o = c as object;
Control x = o as Control;

Is either method preferable and if so why?

[jmcilhinney]

The 'as' keyword doesn't simply cast. It will test the type of the actual object first. If the object is of the type being cast to then the cast is performed. If the object is not of that type then a null reference is returned. If you know for sure that the object is of the type that you're casting to then a straight cast is preferable because it is faster. If the types don't match though, an exception will be thrown, so if there is any doubt about the type of the object then use 'as'. Of course, the MSDN library topic for the C# 'as' keyword would have told you all that.

[wey97]

Of course, the MSDN library topic for the C# 'as' keyword would have told you all that.

I don't keep a local copy and the web site won't connect.

Thanks for the help anyway.

[jmcilhinney]

I don't keep a local copy

You absolutely should. I can't think of any valid reason not to.