Dictionary in C#

Author : Prakash Pradeep Gopu

Dictionary in the c# used to represent a collection of keys and values pair of data.It allows you define the keys and values of any type.It belongs to the generic collection group in c# . The Dictionary type in the C# language provides very fast lookups with keys to get values.

Creating a Dictionary

The Dictionary class is a generic class and can store any data types. This class is defined in the System.Collections.Generic namespace.so If you want to create a dictionary you need to import the “System.Collections.Generic” Name space.

 using System.Collections.Generic;

For creating a dictionary object we will use the new key word.new keyword will allocate the memory. 

Syntax : Dictionary<TKey, TValue> objectname=new Dictionary<TKey, TValue>;

Where TKey -- The type of the keys in the dictionary.

            TValue-- The type of the values in the dictionary.

The following code will create the simple Dictionary and adding values to the Dictionary:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace BloggerExamples

{

    class Dictionaryexample

    {

        static void Main(string[] args)

        {

            // Creating the Dictionary

            Dictionary<string, Int16> NameList = new Dictionary<string, Int16>();

            // Adding the dictionary Item Use Add() method

            NameList.Add("Prakash", 12);

            NameList.Add("Sandeep", 13);

            NameList.Add("Sathya", 14);

            NameList.Add("Sandya", 15);

            // Reading all data in the dictionary

            Console.WriteLine("Name List");

            foreach (KeyValuePair<string, Int16> Names in NameList)

            {

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

            }

         

            //Look up values

            //Checking the key exist or not by using the ContainsKey()

            Console.WriteLine("Look up value for sandeep");

            if (NameList.ContainsKey("Sandeep"))

            {

                // if it exist then lookup the value of sandeep and returns the integer.

                int value = NameList["Sandeep"];

                Console.WriteLine(value);

            }

            Console.Read();

        }

    }

}

OutPut :

Interview Questions :

1) Who is faster hashtable or dictionary ? View Answer

2)  What is Difference between hash table and Dictionary? View Answer