Surely there is a framework method that given an array of integers, strings etc converts them into a list that can be used in a SQL \"IN\" clause?
IN
e.g.
var inClause = "(" + String.Join(",", values.Select(x => x.ToString()).ToArray()) + ")";
Note: You no longer need to call .ToArray() in .NET Framework 4. A new String.Join(string separator, IEnumerable values) method is added.
.ToArray()