How to compare two lists and add the difference to a third list in C#?

First, set the two lists −

List One

List < string > list1 = new List < string > ();
list1.Add("A");
list1.Add("B");
list1.Add("C");
list1.Add("D");

List Two

List < string > list2 = new List < string > ();
list2.Add("C");
list2.Add("D");

To find the difference between the two list and display the difference elements −

IEnumerable < string > list3;
list3 = list1.Except(list2);
foreach(string value in list3) {
   Console.WriteLine(value);
}

The following is the complete example to compare two lists −

Example

using System;
using System.Collections.Generic;
using System.Linq;

public class Demo {
   public static void Main() {
      List < string > list1 = new List < string > ();
      list1.Add("A");
      list1.Add("B");
      list1.Add("C");
      list1.Add("D");

      Console.WriteLine("First list...");
      foreach(string value in list1) {
         Console.WriteLine(value);
      }

      Console.WriteLine("Second list...");
      List < string > list2 = new List < string > ();

      list2.Add("C");
      list2.Add("D");
      foreach(string value in list2) {
         Console.WriteLine(value);
      }

      Console.WriteLine("Difference in the two lists...");
      IEnumerable < string > list3;
      list3 = list1.Except(list2);
      foreach(string value in list3) {
         Console.WriteLine(value);
      }
   }
}