C# - Hashtable Class - Adglob Infosystem Pvt Ltd

The 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.

A hash table is used when you need to access elements by using the 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.

Methods and Properties of the C# Hashtable Class

The following table lists some of the commonly used properties of the Hashtable class −

Sr.No.	Property & Description
1	CountGets the number of key-and-value pairs contained in the Hashtable.
2	IsFixedSizeGets a value indicating whether the Hashtable has a fixed size.
3	IsReadOnlyGets a value indicating whether the Hashtable is read-only.
4	ItemGets or sets the value associated with the specified key.
5	KeysGets an ICollection containing the keys in the Hashtable.
6	ValuesGets an ICollection containing the values in the Hashtable.

The following table lists some of the commonly used methods of the Hashtable class −

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

Example

The following example demonstrates the concept −

using System;
using System.Collections;

namespace CollectionsApplication {
   class Program {
      static void Main(string[] args) {
         Hashtable ht = new Hashtable();
         
         ht.Add("001", "Zara Ali");
         ht.Add("002", "Abida Rehman");
         ht.Add("003", "Joe Holzner");
         ht.Add("004", "Mausam Benazir Nur");
         ht.Add("005", "M. Amlan");
         ht.Add("006", "M. Arif");
         ht.Add("007", "Ritesh Saikia");
         
         if (ht.ContainsValue("Nuha Ali")) {
            Console.WriteLine("This student name is already in the list");
         } else {
            ht.Add("008", "Nuha Ali");
         }
         
         // Get a collection of the keys.
         ICollection key = ht.Keys;
         
         foreach (string k in key) {
            Console.WriteLine(k + ": " + ht[k]);
         }
         Console.ReadKey();
      }
   }
}

When the above code is compiled and executed, it produces the following result −

001: Zara Ali
002: Abida Rehman
003: Joe Holzner
004: Mausam Benazir Nur
005: M. Amlan
006: M. Arif
007: Ritesh Saikia
008: Nuha Ali

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