Dictionaries and Hash Table in C#

This article explains the concept of dictionaries in C#, from the basics to the level afterwards I'll explain the concept of types of dictionaries and the concept of a hash table and it's related useful operations with their respective example.

Dictionaries

• Dictionaries are used to associate a specific 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 sets of members in their declaration.
  
  
  

Now to explain hash tables.

Hash Table | Dictionaries

• A Hash Table is an example of a 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 a hash table are:



Add Operation | Hash Table

Adding Data to the Hash Table

There are two methods to add data to your hash table in C#, you can both use or any of them in your code. I'll show both methods with an example.

Method 1

In method 1 for adding data we use:

HT.Add("CShub", "cshub.somee.com");
HT.Add("GoogleSays", "jaiswalabhishek.blogspot.in");
HT.Add("Picmaniac", "picmaniac.brinkster.net");

Method 2

In method 2 we 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();

}

}

}



The following is the second method for the 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 in other languages, in C# count is used for counting the total number of data values available in the hash table.

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

A 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

A Remove operation is used for removing data entries from your hash table. This is simply performed 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();

}

}

}