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Introduction to var datatype in C#

By Rekha Singh on Aug 11, 2009
This article introduces us to var datatype in C#.

var Type: 

  • C# 3.0 adds the interesting behavior of Declaring Local Variables Implicitly. This means that there is no need to mention the data type when declaring a variable. A local variable can be declared implicitly using the var keyword in C#.

  • Declaring local variables implicitly has some restrictions; the variable must be initialized to some expression that can not be null.

    var a= 10;
    var z = "Rekha";

  • The primary reason for its existence is the introduction of anonymous types in C#

  • Another point to stress is that variable inference does not work for class level fields or method arguments or anywhere else other than for local variables in a method.

Advantages :

  • Less typing with no loss of functionality

  • Increases the type safety of your code. A foreach loop using an iteration variable which is typed to var will catch silently casts that are introduced with explicit types

  • Makes it so you don't have to write the same name twice in a variable declaration.

  • Some features, such as declaring a strongly typed anonymous type local variable, require the use of var

Example 1:

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

namespace Namesp1
    class Program
        static void Main(string[] args)
            var x = Convert.ToInt32(Console.ReadLine());
            var y = Convert.ToInt32(Console.ReadLine());
            Console.WriteLine("The Sum Is : " + (x + y));

Example 2:

namespace ConsoleApplication1
    class A
        public static void Main()
            int sum = 0;
            int[] arr = new int[10];
            for (int i = 0; i < 10; i++)
                arr[i] = i;
            foreach (var x in arr)
                Console.WriteLine("Value is: " + x);
                sum =sum + x;
            Console.WriteLine("Sum of array elements is : " + sum);





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