Dictionary in C#, VB.NET with Examples

By: Suresh Dasari Aug 24, 2016

Introduction:

Here I will explain what is dictionary in c#, vb.net with example or dictionary object in c#, vb.net with example or how to create and use dictionary object in c#, vb.net with example. Dictionary object in c# or vb.net is a collection which is used to represent data as a key and value pairs.

Description:

In previous posts I explained difference between array list and list in c#, vb.net, connection pooling in asp.net with examples, difference between initialization and instantiation in c#, vb.net, cursor in sql server with examples, difference between char varchar nvarchar in sql, difference between ref and out in c#, vb.net with example and many articles related to interview questions, asp.net, c#.net. Now I will explain what is dictionary object in c#, vb.net with example.

Dictionary Object

Dictionary is a collection object which is used to store data in key and value pairs. In dictionary object Key value must be always unique and it won’t accept any null or duplicate values because we use keys to identify values stored in dictionary object but values can be duplicated or we can set null value also.

The Dictionary collection is a part of generic collections so to use Dictionary object in our applications we need to add following namespace in our applications.

C# Code

using System.Collections.Generic;

VB.NET Code

Imports System.Collections.Generic

We will see the syntax of using Dictionary object in our applications.

Syntax of Dictionary Object

Following is the syntax of using Dictionary object in our applications.

Dictionary<TKey,TValue>

The Dictionary class will accept two parameters one is for key and another for value.

TKey – It defines what type of keys which we are going to store.

TValue – It defines what type of values which we are going to store.

Following is the declaration of Dictionary object

Dictionary<int,string>

The dictionary object can be initialized with IDictionary<TKey,TVal> interface or Dictionary<TKey,TVal> class like as shown below

C# Code

IDictionary<int, string> objdict = new Dictionary<int, string>();

//or

Dictionary<int, string> objdict = new Dictionary<int, string>();

VB.NET Code

Dim objdict As IDictionary(Of Integer, String) = New Dictionary(Of Integer, String)()

'or

Dim objdict As New Dictionary(Of Integer, String)()

It’s always recommended to use IDictionary<TKey,TVal> interface instead of Dictionary<TKey,TVal> class.

We will see how to add elements to Dictionary object and how to access Dictionary object elements with example.

Example of Dictionary Object

Following is the example of using Dictionary object in our applications.

C# Code

using System;

using System.Collections.Generic;

namespace Linqtutorials

{

class Program

{

static void Main(string[] args)

{

// Adding Elements to Dictionary Object

IDictionary<int, string> objdic = new Dictionary<int, string>();

objdic.Add(1, "Suresh Dasari");

objdic.Add(2, "Rohini Alavala");

objdic.Add(3, "Praveen Alavala");

objdic.Add(4, "Sateesh Chandra");

// Read Data from Dictionary Object

Console.WriteLine("Number of Users: {0}", objdic.Count);

Console.WriteLine("User Details");

foreach (KeyValuePair<int, string> user in objdic)

{

Console.WriteLine("Key={0}, Value={1}", user.Key, user.Value);

}

Console.ReadLine();

}

VB.NET Code

Module Module1

Sub Main()

' Adding Elements to Dictionary Object

Dim objdic As IDictionary(Of Integer, String) = New Dictionary(Of Integer, String)()

objdic.Add(1, "Suresh Dasari")

objdic.Add(2, "Rohini Alavala")

objdic.Add(3, "Praveen Alavala")

objdic.Add(4, "Sateesh Chandra")

' Read Data from Dictionary Object

Console.WriteLine("Number of Users: {0}", objdic.Count)

Console.WriteLine("User Details")

For Each user As KeyValuePair(Of Integer, String) In objdic

Console.WriteLine("Key={0}, Value={1}", user.Key, user.Value)

End Sub

End Module

If you observe above example we are adding elements to Dictionary object “objdic” and getting elements from Dictionary object “objdic” using “KeyValuePair<TKey, TVal>”. Now we will run and see the output that would be like as shown below.

Output of Dictionary Object Example

Following is the result of Dictionary object example.

Dictionary object in c#, vb.net with example

In Dictionary object we have different properties and methods available to perform like getting count or elements or check elements in Dictionary object or get particular value from dictionary object with key value, etc.

Dictionary Object Properties

Following are the properties available in dictionary object.

Property	Description
Comparer	It is used to determine equality of keys
Count	It is used to get number of elements exists in Dictionary<TKey,TVal>
Item	It’s used to gets or sets the value associated with the specified key.
Keys	It’s used to get collection containing keys in the Dictionary<TKey,TValue>.
Values	It’s used to get a collection containing the values in the Dictionary<TKey,TValue>.

Dictionary Object Methods

Following are the methods available in dictionary object.

Method	Description
Add(TKey,TVal)	It is used to add specified key and value to the dictionary
Remove(TKey)	Removes the value from Dictionary<TKey, TValue> based on specified key
TryGetValue(TKey, TValue)	It is used to get the value associated with the specified key.
Clear	It removes all keys and values from the Dictionary<TKey, TValue>.
ContainsKey(TKey)	It determines whether the Dictionary<TKey, TValue> contains specified key or not.