>>It's Linq. Think it came in .NET 3.5 ?
>>Even simpler, BTW :

bool isWithin = cstring.Split(',').Contains(iNumber.ToString());

>
>Again, thank you very much. As I just mentioned to Gregory, I can't seem to see the Contains in my list of methods (in Intellisense).

You need to add LINQ reference to the using statement. Try pressing ctrl+dot after you typed Contains and see if it suggests you the using statement.