C# program to find Union of two or more Dictionaries

Firstly, set both the dictionaries −

Dictionary < string, int > dict1 = new Dictionary < string, int > ();
dict1.Add("water", 1);
dict1.Add("food", 2);
Dictionary < string, int > dict2 = new Dictionary < string, int > ();
dict2.Add("clothing", 3);
dict2.Add("shelter", 4);

Now, create HashSet and use UnionsWith() method to find the union between the above two Dictionaries −

HashSet < string > hSet = new HashSet < string > (dict1.Keys);
hSet.UnionWith(dict2.Keys);

The following is the complete code −

Example

using System;
using System.Collections.Generic;

public class Program {
   public static void Main() {
      Dictionary < string, int > dict1 = new Dictionary < string, int > ();
      dict1.Add("water", 1);
      dict1.Add("food", 2);

      Dictionary < string, int > dict2 = new Dictionary < string, int > ();
      dict2.Add("clothing", 3);
      dict2.Add("shelter", 4);

      HashSet < string > hSet = new HashSet < string > (dict1.Keys);
      hSet.UnionWith(dict2.Keys);

      Console.WriteLine("Union of Dictionary...");
      foreach(string val in hSet) {
         Console.WriteLine(val);
      }
   }
}

Output

Union of Dictionary...
water
food
clothing
shelter