C# Program to combine Dictionary of two keys

Firstly, set the Dictionaries to be combined −

Dictionary <string, int> dict1 = new Dictionary <string, int> ();
dict1.Add("one", 1);
dict1.Add("Two", 2);
Dictionary <string, int> dict2 = new Dictionary <string, int> ();
dict2.Add("Three", 3);
dict2.Add("Four", 4);

Now, use HashSet to combine them. The method used for the same purpose is UnionWith() −

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

The following is the complete code −

Example

 Live Demo

using System;
using System.Collections.Generic;
public class Program {
   public static void Main() {
      Dictionary <string, int> dict1 = new Dictionary <string, int> ();
      dict1.Add("one", 1);
      dict1.Add("Two", 2);
      Dictionary <string, int> dict2 = new Dictionary <string, int> ();
      dict2.Add("Three", 3);
      dict2.Add("Four", 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...
one
Two
Three
Four