CSharp Topic

Dot Net Basic
HashTable class:-
  • 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.


Methods and Properties of HashTable class:-

Methods of HashTable class:-

Sr.No. Method
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.


Properties of HashTable class:-

Property Description
Count Gets the number of key-and-value pairs contained in the Hashtable.
IsFixedSize Gets a value indicating whether the Hashtable has a fixed size.
IsReadOnly Gets a value indicating whether the Hashtable is read-only.
Item Gets or sets the value associated with the specified key.
Keys Gets an ICollection containing the keys in the Hashtable.
Values Gets an ICollection containing the values in the Hashtable.


Hashtable Example:- 

 
using System;
using System.Collections;
class HashTableDemo
{
    public HashTableDemo()
    {
        Console.WriteLine("This is hash table demo::\n");
    }
    public void Show()
    {
        Hashtable ht = new Hashtable();

        ht.Add("001", "Santosh kumar singh");
        ht.Add("002", "Gagan");
        ht.Add("003", "Manorma arya");
        ht.Add("004", "Reena kumari");
        ht.Add("005", "Anjanee kumar singh");
        ht.Add("006", "Pramod kumar sah");
        ht.Add("007", "Laxmi Pati Ojha");
        ht.Add("008", "Chandan kumar");

        if (ht.ContainsValue("Rajeev kumar"))
        {
            Console.WriteLine("This student name is already in the list");
        }
        else
        {
            ht.Add("009", "Rajeev kumar");
        }

        // Get a collection of the keys.
        ICollection key = ht.Keys;

        foreach (string k in key)
        {
            Console.WriteLine(k + ": " + ht[k]);
        }

       
    }
}

class Test
{
    static void Main(string[] args)
    {
         HashTableDemo objHT = new  HashTableDemo();
        objHT.Show();
        Console.ReadLine();
    }
}