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Understand Generic Collections in C# with an example

• By Gurunatha Dogi in C#
• Dec 7th, 2013
• 49084
• 7

Generic Collections

In our previous article we saw on generics and how we separated the data-type logic from a logical code snippet using generics. Taking forward that same logic, means separating collection logic i.e (Add, Search, Remove, Clear) from data-type, we will see different types of generic collections available in .net.

We can use generic collections in our code by calling the namespace "using System.Collections.Generic".

Generic Collections helps us to create flexible type-safe, strong type collections at compile time.

Generic collections helps us to separate the collection logic (Add, Search, Remove, Clear) from different data-types available in .net.

Why Generic Collections

There are already different types of dotnet collections available in .net like array, arraylist, hashtables and specialized collections (string collections, hybrid collections) each of these collections have their own strong point and weak point.

For example:

Arrays are strong types so there are no boxing and unboxing but weak point of this is it of fixed length size means it is not flexible.

Arraylists and Hashtables are flexible in size but they are not strong type collections, we can pass any data-type objects to it, means there are lots of boxing and unboxing which means slow in performance.

So by keeping in this mind dotnet development team has brought Generic Collections which bridges advantages of both strong type and dynamically resize and at a same time to pass any data-type to collections logic.

Development team applied generic concept on dotnet collections

• .NET collections to make generic collections.
• Arraylist to make list generic collections.
• Hashtables to make Dictionary.
• Stacks and Queues to make Stacks and Queues generics.

All these above collections available in "using System.Collections.Generic" namespace.

Types of Generic Collections

Generic List Collection

List collection are strong type index based collection and dynamically resizable and at a same time we can pass any data type to a list object. It provides many inbuilt methods to manipulate list object. List generic collections is a generic concept applied over Arrays and Arraylist.

Syntax

 
List obj = new List();

Where "T" generic parameter you can pass any data-type or custom class object to this parameter.

Example

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace GenericCollections
{
    class Program
    {
        static void Main(string[] args)
        {

            List list = new List();

            list.Add(1);
            list.Add(2);
            list.Add(9);

            foreach (int numbers in list) 
            {
                Console.WriteLine(numbers);
            }

            Console.WriteLine("Count -> {0}",list.Count); 
            Console.WriteLine("\n-------------------------------------------\n");

            List list1 = new List();

            list1.Add(false);
            list1.Add(true);
            list1.Add(true);
            list1.Add(false);

            foreach (bool booleans in list1)
            {
                Console.WriteLine(booleans);
            }

            Console.WriteLine("Count -> {0}", list1.Count); 
            Console.WriteLine("\n-------------------------------------------\n");

            List list2 = new List();

            list2.Add("Khadak");
            list2.Add("Shiv");
            list2.Add("Shaam");
            list2.Add("Pradeep Dhuri");

            foreach (string stringnames in list2)
            {
                Console.WriteLine(stringnames);
            }

            Console.WriteLine("Count -> {0}", list2.Count); 

            Console.WriteLine("\n-------------------------------------------\n");
        }
    }
}

Output

Generic Dictionary in C-sharp

Dictionary is a generic collections which works on key and value pairs. Both key and value pair can have different data-types or same data-types or any custom types (i.e. class objects). Dictionary generic collections is a generic concept applied over Hashtable and it provides fast lookups with keys to get values.

Syntax

 
Dictionary obj = new List();

Dictionary Represents a collection of keys and values.

Where "TKey" and "TValue" are generic parameters you can pass any data-type or custom class object to this parameters.

 
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace GenericCollections
{
    class Program
    {
        static void Main(string[] args)
        {

            
            Dictionary animaldictionary = new Dictionary();
            animaldictionary.Add("Tiger", 3);
            animaldictionary.Add("Lion", 2);
            animaldictionary.Add("Panda", 1);


            foreach (KeyValuePair pair in animaldictionary)
            {
                Console.WriteLine("{0}, {1}", pair.Key, pair.Value);
            }

            Console.WriteLine("\n-------------------------------------------\n");

            foreach (var pair in animaldictionary)
            {
                Console.WriteLine("{0}, {1}", pair.Key, pair.Value);
            }



           
        }
    }
}

Output

Generic Stack and Queue

Generic Stack and Queue is a concept applied over dot net collection stack and queue. Generic Stack and Queue naming coventions are similar to dot net collection stack and queue but it has got additional generic parameter "" to pass any data-type. Generic Stack will represents a last-in-first-out (LIFO) principle from collection of objects and Generic Queue will represents a first-in, first-out (FIFO) principle from collection of objects. Means when you remove any item from generic stack collections then the last or recently or new added item will be removed first like it will work in reverse order. While when you remove any item from generic queue collection then the first added item will be removed from generic queue collections.

Stack works on (Last in first out principle - LIFO) on principle and uses "Push()" method to add items to the collections and "Pop()" method to remove any item from the collections.

Queue works on (First in First out - FIFO) principle and uses "Enqueue()" method to add items to the collections and "Dequeue()" method to remove any item from the collections.

Syntax

 
Stack objstack = new Stack();
Queue  objqueue = new Queue ();

Example

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace GenericCollections
{
    class Program
    {
        static void Main(string[] args)
        {

            //Declaring Stack
            Stack stacknum = new Stack();
            stacknum.Push(1);
            stacknum.Push(2);
            stacknum.Push(3);
            stacknum.Push(5);
	     stacknum.Push(6);



            foreach (int numbers in stacknum)
            {
                Console.WriteLine("Stack Numbers {0}", numbers);
            }
		
	     stacknum.Pop(); //It will remove last/recent added element from the collections i.e (6)


            Console.WriteLine("\n-------------------------------------------\n");

             //Declaring Stack
            Stack stacknames = new Stack();
            stacknames.Push("Pradeep Dhuri");
            stacknames.Push("Shiv Prasad");
            stacknames.Push("Khadak");
            stacknames.Push("Shaam");


            foreach (string strnames in stacknames)
            {
                Console.WriteLine("Stack Names {0}", strnames);
            }
		
	     stacknames.Pop(); //It will remove last element/recent added element from the collections i.e. Shaam

	     Console.WriteLine("\n-------------------------------------------\n");

		
	    //Declaring Queue
            Queue Queuenum = new Queue();
            Queuenum.Enqueue(1);
            Queuenum.Enqueue(2);
            Queuenum.Enqueue(3);
            Queuenum.Enqueue(5);
	     Queuenum.Enqueue(6);



            foreach (int numbers in Queuenum)
            {
                Console.WriteLine("Queue Numbers {0}", numbers);
            }
		
	     Queuenum.Dequeue(); //It will remove first element from the collections i.e (1)


            Console.WriteLine("\n-------------------------------------------\n");


	      //Declaring Queues
            Queue  Queuenames = new Queue();
            Queuenames.Enqueue("Mohan Aiyer");
            Queuenames.Enqueue("Shiv Prasad");
            Queuenames.Enqueue("Khadak");
            Queuenames.Enqueue("Shaam");


            foreach (string strnames in Queuenames)
            {
                Console.WriteLine("Queue Names {0}", strnames);
            }
		
	     Queuenum.Dequeue(); //It will remove first added element from the collections i.e Mohan Aiyer

	     Console.WriteLine("\n-------------------------------------------\n");


           
        }
    }
}

Hey friend, hope you understand generic collections in C#. If you have any doubts or queries kindly let me know through your valuable comments/feedback. If you like this article kindly share it in your friends circle.

Gurunatha Dogi

Gurunatha Dogi is a software engineer by profession and founder of Onlinebuff.com, Onlinebuff is a tech blog which covers topics on .NET Fundamentals, Csharp, Asp.Net, PHP, MYSQL, SQL Server and lots more..... read more

Comments

By Ramakrishna on 2014-12-02

Excellent... ***** 5/5 Rating

By Ramakrishna on 2014-12-02

Excellent Concept..I dont know how fresher's will understand this.. but if you have quite good grip on C# and need to improve or to recollect its "THE BEST" tutorial..*****(5/5 Rating)..

By Dasharath on 2014-09-03

Syntax List obj = new List(); wrong syntax, please rectify. Accuracy is very important otherwise people will ignore such good article.

By Sri on 2014-08-19

excellent super..... no words to say

By Sri on 2014-08-19

plz give the .net framework version in which each feature introduced

By Admin on 2014-04-23

Hey #Dilip Verma, Sorry about typing mistake, It will remove the name "Mohan Aiyer" not the "Pradeep Dhuri" typing mistake.

By Dilip verma on 2014-04-22

hey in this code Queue name section you can delete the name of first but this one is not insert in queue list then how to delete this element Pradeep Dhuri this one is not insert in queue Queue Queuenames = new Queue(); Queuenames.Enqueue("Mohan Aiyer"); Queuenames.Enqueue("Shiv Prasad"); Queuenames.Enqueue("Khadak"); Queuenames.Enqueue("Shaam"); foreach (string strnames in Queuenames) { Console.WriteLine("Queue Names {0}", strnames); } Queuenum.Dequeue(); //It will remove first added element from the collections i.e Pradeep Dhuri