C# Program to find a key in a Hashtable

Set Hashtable collection with elements.

Hashtable h = new Hashtable();
h.Add(1, "Jack");
h.Add(2, "Henry");
h.Add(3, "Ben");
h.Add(4, "Chris");

Let’s say now you need to find any key, then use the Contains() method. We are finding key 3 here −

h.Contains(3);

The following is the complete example.

Example

 Live Demo

using System;
using System.Collections;
public class Demo {
   public static void Main() {
      Hashtable h = new Hashtable();
      h.Add(1, "Jack");
      h.Add(2, "Henry");
      h.Add(3, "Ben");
      h.Add(4, "Chris");
      Console.WriteLine("Keys and Values list:");
      foreach (var key in h.Keys ) {
         Console.WriteLine("Key = {0}, Value = {1}",key , h[key]);
      }
      Console.WriteLine("Key 3 exists? "+h.Contains(3));
   }
}

Output

Keys and Values list:
Key = 4, Value = Chris
Key = 3, Value = Ben
Key = 2, Value = Henry
Key = 1, Value = Jack
Key 3 exists? True