Wednesday, March 14, 2012

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 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 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"];




OutPut :

Interview Questions :

1) Who is faster hashtable or dictionary ? View Answer
2)  What is Difference between hash table and Dictionary? View Answer

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