It might help you,
class Program
{
static void Main(string[] args)
{
var result = Intersect();
Console.WriteLine(result);
}
private static string Intersect()
{
string test1 = "a,b,c,d,e";
string test2 = "b,e";
return string.Join(",", test1.ToArray().Where(item => !test2.Contains(item.ToString())).ToArray());
}
}
:)