How to use Dictionary in c# .NET with example ?

Dictionary in c#

As Dictionary work with two type of data (one for ‘key’ and one for ‘value’), it requires both these data types to be defined at the time of initialization. Also, the namespace “System.Collections.Generic” is required for using dictionary in your application.

A Dictionary class is a data structure that represents a collection of keys and values pair of data. The key is identical in a key-value pair and it can have at most one value in the dictionary, but a value can be associated with many different keys.

This class is defined in the System.Collections.Generic namespace, so you should import or using System.Collections.Generic namespace.


Syntex:-

Dictionary<KeyObject, ValueObject> DicObj = new Dictionary<KeyObject, ValueObject>();

Initialize A Dictionary Object In C#:

Dictionary<string, string> DicObj = new Dictionary<string, string>();

Methods:-

1.  DicObj.Add(index, item);    // to add into Dictionary

2.  DicObj.Remove(index);       // to Remove from  Dictionary

3. DicObj.Clear();                     // to Clear all Key/Values from  Dictionary



 // to determine the existence of Item in  Dictionary

1. 1Bool  IsExist = DicObj.ContainsKey(index);
2. Bool   IsExist  = DicObj.ContainsValue(item);

Traverse and display Dictionary  Items:-

foreach( KeyValuePair<string, string> item in DicObj)
     {
           Console.Write(item.Key +"   "+ item.Value);
            Console.Write("\n");

     }

Source code in c#:-

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace ConsoleAppDemo

{

    class Program

    {

        static void Main(string[] args)

        {

            Dictionary_Operations classObj = new Dictionary_Operations();

            while (true)

            {

                // Console.Clear();

                Console.WriteLine("\n");

                Console.WriteLine("1. Add an Item");

                Console.WriteLine("2. Remove a Item");

                Console.WriteLine("3. Display Dictionary Items");

                Console.WriteLine("4. Search Items by Key");

                Console.WriteLine("5. Search Items by Value");

                Console.WriteLine("6. Exit");

                Console.Write("Select your choice: ");

                int choice = Convert.ToInt32(Console.ReadLine());

                switch (choice)

                {

                    case 1:

                        classObj.Add();

                        break;

                    case 2: classObj.RemoveItem();

                        break;

                  

                    case 3: classObj.Display();

                        break;

                    case 4: classObj.SearchByKey();

                        break;

                    case 5: classObj.SearchByValue();

                        break;

                    case 8: System.Environment.Exit(1);

                        break;

                }

                Console.ReadKey();

            }

        }

    }

    public class Dictionary_Operations

    {

        string item;

        string index;

        bool IsExist = false;

        Dictionary<string, string> DicObj = new Dictionary<string, string>();

        // Add an Item to Dictionary

        public void Add()

        {

            Console.WriteLine("\nEnter a Index to Add an Item");

            index = Console.ReadLine();

            Console.WriteLine("\nEnter a Item to Add");

            item = Console.ReadLine();

            DicObj.Add(index, item);

             Console.Write("\nAdded successfully! \n");

        }

      

        //remove an item at any given index

        public void RemoveItem()

        {

            Console.WriteLine("\nEnter a Index to Remove an Item");

            index = Console.ReadLine();

            DicObj.Remove(index);

            Console.Write("\nItem Removed successfully!: \n");

           

        }

        //Search Item by using Key

        public void SearchByKey()

        {

            Console.WriteLine("\nEnter a Index to Search an Item");

            index = Console.ReadLine();

           IsExist= DicObj.ContainsKey(index);

           if (IsExist)

            Console.Write("\nItem Found!: \n");

           else

               Console.Write("\nItem Not found!: \n");

        }

        //Search Item by using Item Value

        public void SearchByValue()

        {

            Console.WriteLine("\nEnter a Item Value to Search");

            item = Console.ReadLine();

            IsExist = DicObj.ContainsValue(item);

            if (IsExist)

                Console.Write("\nItem Found!: \n");

            else

                Console.Write("\nItem Not found!: \n");

        }

        // Display Items in the Dictionary

        public void Display()

        {

            Console.Write("\nItems in the List are: \n");

            Console.Write("\n");

            Console.Write("\nKey" + "   " + "value\n");

            Console.Write("\n");

            foreach( KeyValuePair<string, string> item in DicObj)

            {

                Console.Write(item.Key +"   "+ item.Value);

               Console.Write("\n");

            }

        }

      

    }

}

Output:-

Output Listing 1:-

Output Listing 2:-

Output Listing 3:-

Output Listing 4:-

Output Listing 5:-

Output Listing 6:-