Regular Expressions for password

public static bool IsValidPassword (string input)
        {
Match match = Regex.Match(input, @"(?=^.{8,12}$)((?=.*\d)(?=.*[A-Z])(?=.*[a-z])|(?=.*\d)(?=.*[^A-Za-z0-9])(?=.*[a-z])|(?=.*[^A-Za-z0-9])(?=.*[A-Z])(?=.*[a-z])|(?=.*\d)(?=.*[A-Z])(?=.*[^A-Za-z0-9]))^.*");

            if (match.Success && match.Index == 0 && match.Length == input.Length)
				return true;
			else
				return false;

        }