What is the Hashtable class in C#?

Hashtable class represents a collection of key-and-value pairs that are organized based on the hash code of the key. It uses the key to access the elements in the collection.

Some of the commonly used methods in Hashtable class are −

Sr.No.Method & Description
1public virtual void Add(object key, object value);
Adds an element with the specified key and value into the Hashtable.
2public virtual void Clear();
Removes all elements from the Hashtable.
3public virtual bool ContainsKey(object key);
Determines whether the Hashtable contains a specific key.
4public virtual bool ContainsValue(object value);
Determines whether the Hashtable contains a specific value.

The following is an example showing the usage of Hashtable class in C#.


 Live Demo

using System;
using System.Collections;
namespace Demo {
   class Program {
      static void Main(string[] args) {
         Hashtable ht = new Hashtable();
         ht.Add("D01", "Finance");
         ht.Add("D02", "HR");
         ht.Add("D03", "Operations");
         if (ht.ContainsValue("Marketing")) {
            Console.WriteLine("This department name is already in the list");
         } else {
            ht.Add("D04", "Marketing");
         ICollection key = ht.Keys;
         foreach (string k in key) {
            Console.WriteLine(k + ": " + ht[k]);

Above we have used the Hashtable class add() method to add elements with the key and value pair.

Hashtable ht = new Hashtable();

ht.Add("D01", "Finance");
ht.Add("D02", "HR");
ht.Add("DO3", "Operations");


D04: Marketing
D02: HR
D03: Operations
D01: Finance