C# program to find Union of two or more Lists

Firstly, create lists −

//three lists
var list1 = new List{3, 4, 5};
var list2 = new List{1, 2, 3, 4, 5};
var list3 = new List{5, 6, 7, 8};

Use the union method to get the union of list1 and list2 −

var res1 = list1.Union(list2);
var res2 = res1.Union(list3);

The following is the complete code −

Example

 Live Demo

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

public class Demo {
   public static void Main() {
      //three lists
      var list1 = new List<int>{3, 4, 5};
      var list2 = new List<int>{1, 2, 3, 4, 5};
      var list3 = new List<int>{5, 6, 7, 8};

      // finding union
      var res1 = list1.Union(list2);
      var res2 = res1.Union(list3);

      foreach(int i in res2) {
         Console.WriteLine(i);
      }
   }
}

Output

3
4
5
1
2
6
7
8