How can get difference between two lists?

List<string> First = new List<string>();
          First.Add("A");
          First.Add("D");
          First.Add("B");
          First.Add("C");

          List<string> List = new List<string>();

          List.Add("C");
          List.Add("B");


          IEnumerable<string> Third ;
          Third = First.Except(List);

string[] names1 = System.IO.File.ReadAllLines(@"../../../names1.txt");
        string[] names2 = System.IO.File.ReadAllLines(@"../../../names2.txt");

        // Create the query. Note that method syntax must be used here.
        IEnumerable<string> differenceQuery =
          names1.Except(names2);

        // Execute the query.
        Console.WriteLine("The following lines are in names1.txt but not names2.txt");
        foreach (string s in differenceQuery)
            Console.WriteLine(s);

        // Keep the console window open in debug mode.
        Console.WriteLine("Press any key to exit");
        Console.ReadKey();</string>

List<object> Items = new List<object>();

foreach(object obj in List1)
{

if(!List2.Contains(obj))
{

Items.Add(obj);

}

}