The 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.

A hash table is used when you need to access elements by using key, and you can identify a useful key value. Each item in the hash table has a key/value pair. The key is used to access the items in the collection.

Creating hash table

Hashtable ht =new Hashtable();
This code will create hash table with named ht.

Adding items to hash table

ht.Add(“001”,”Sachin”);

ht.Add(“002”,”Rahul”);

This code will add items to hash table, it uses add() method and has key and value parameters.

Retrieving an item value in hash table

string name=ht[001].ToString();

This code will retrieve the item value.

Removing item from hash table

ht.Remove(“001”);

This code will remove the item from the hash table with key value 001.

Example

using System;
using System.Collections;
namespace HashTableConsoleApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            Hashtable ht = new Hashtable();
            Console.Write("Enter Maximum Number Of Record To Be In Hashtable = ");
            int max = Convert.ToInt32(Console.ReadLine());
 
            for (int i = 1; i <= max; i++)
            {
                Console.Write("Enter Data =");
                string data = Console.ReadLine();
                ht.Add(i, data);
            }
            ICollection key = ht.Keys;
            Console.WriteLine("\n\nData in Hashtable");
            foreach (int k in key)
            {
                Console.WriteLine(k + ":" + ht[k]);
            }
        }
    }
}

Output