[c#] Checking if a string array contains a value, and if so, getting its position

EDIT: I hadn't noticed you needed the position as well. You can't use IndexOf directly on a value of an array type, because it's implemented explicitly. However, you can use:

IList<string> arrayAsList = (IList<string>) stringArray;
int index = arrayAsList.IndexOf(value);
if (index != -1)
{
    ...
}

(This is similar to calling Array.IndexOf as per Darin's answer - just an alternative approach. It's not clear to me why IList<T>.IndexOf is implemented explicitly in arrays, but never mind...)