Dictionaries and Hash Table in C#

In this article am going to explain you concept of dictionaries in C#, from base to the level afterwards I’ll be discussing about the concept of types of dictionaries and concept of hash table and it’s related useful operation with their respective example.

Dictionaries

·        -   Dictionaries are used to associate a particular key with a given value.

·        -   Dictionaries are collection classes.

·        -   Functionality or access to the dictionary in C# is provided using-
    using System.Collections;

·         -  A dictionary uses KEYS, for their functioning.

·         -  Dictionaries don’t have any sense of order.

·         -  Keys, works as lookups for table.

·         -  A dictionary contains various set of members in its declaration.

Now am going to discuss about hash table.

Hash Table | Dictionaries

·         -  Hash Table is an example of dictionary.

·         -  Declared in the same fashion as you declare other classes in C#.

·         -  Declared using this function
            Hashtable HT = new Hashtable();

·         This will create a new hash table, in which you can add data and perform other operations.

Operations | Hash Table

The major operations of hash table are-

 - Add
 - Remove
 - Copy
 - Count
 - Test

Add Operation | Hash Table

Adding Data to the Hash Table

There are two methods of adding data in your hash table in C#, you can both use or any of them in your code. I’ll show both methods through example.

Method: 1

In method 1 for adding data we do use-
            HT.Add("CShub", "cshub.somee.com");

            HT.Add("GoogleSays", "jaiswalabhishek.blogspot.in");

            HT.Add("Picmaniac", "picmaniac.brinkster.net"); 

Method: 2

In method2 we do use-
            HT["GoogleSays"] = "jaiswalabhishek.blogspot.in";

            HT["CShub"] = "cshub.somee.com";

Example | Hash Table

using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace Hello_Word

{

    class Program

    {

        static void Main(string[] args)

        {

            Hashtable HT = new Hashtable();

            HT.Add("CShub", "cshub.somee.com");

            HT.Add("GoogleSays", "jaiswalabhishek.blogspot.in");

            HT.Add("Picmaniac", "picmaniac.brinkster.net"); 

            Console.WriteLine("Address for website {0} is {1}  ", "GoogleSays", HT["GoogleSays"]);

            Console.ReadLine();

        }

     }

}

This is the second method for same functionality-

using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace Hello_Word

{

    class Program

    {

        static void Main(string[] args)

        {

            Hashtable HT = new Hashtable();

           // HT.Add("CShub", "cshub.somee.com");

           // HT.Add("GoogleSays", "jaiswalabhishek.blogspot.in");

           // HT.Add("Picmaniac", "picmaniac.brinkster.net"); 

            HT["GoogleSays"] = "jaiswalabhishek.blogspot.in";

            HT["CShub"] = "cshub.somee.com";

            Console.WriteLine("Address for website {0} is {1}  ", "GoogleSays", HT["GoogleSays"]);

            Console.ReadLine();

        }

     }

}

Count Operation | Hash Table

§  -   As like other languages in C# count is used for counting total number of data values available in the hash table.

§ -   There is no sense of order in the hash table for this operation.

§ -   Count operation is performed by-
Console.WriteLine("Total websites of abhishek jaiswal are {0}", HT.Count);

Example | Count

using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace Hello_Word

{

    class Program

    {

        static void Main(string[] args)

        {

            Hashtable HT = new Hashtable();

            HT.Add("CShub", "cshub.somee.com");

            HT.Add("GoogleSays", "jaiswalabhishek.blogspot.in");

            HT.Add("Picmaniac", "picmaniac.brinkster.net"); 

           // Console.WriteLine("Address for website {0} is {1}  ", "GoogleSays", HT["GoogleSays"]);

            Console.WriteLine("Total websites of abhishek jaiswal are {0}", HT.Count);

            Console.ReadLine();

        }

     }

}

Remove Operation | Hash Table

Remove operation is used for removing data entries from your hash table. This is simply performed by using-
            HT.Remove("GoogleSays");

Example | Remove

using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace Hello_Word

{

    class Program

    {

        static void Main(string[] args)

        {

            Hashtable HT = new Hashtable();

            HT.Add("CShub", "cshub.somee.com");

            HT.Add("GoogleSays", "jaiswalabhishek.blogspot.in");

            HT.Add("Picmaniac", "picmaniac.brinkster.net");

            HT.Remove("GoogleSays");

            if (HT.ContainsKey("GoogleSays"))

            {

                Console.WriteLine("Address for website {0} is {1}  ", "GoogleSays", HT["GoogleSays"]);

                // Console.WriteLine("Total websites of abhishek jaiswal are {0}", HT.Count);

            }

            Console.ReadLine();

        }

     }

}