
The **“var”** keyword shifts the responsibility of selecting the data type of a variable from the programmer to the compiler. How? 
* If the “var” keyword is used before the name of a variable, its type **need not** be defined. 
* When the code is run, the compiler decides the data type for the variable itself. 

A “var” type variable **cannot** be null. It must always have a value. Think of it this way- you can’t keep a hidden object on the desk and guess what it is. The same way, you can't have a null variable and expect the compiler to decide its data type.




Usually, the “var” keyword is used when the data type of the variable is exceptionally long and it's tedious to keep repeating it. Moreover, in array lists when there are elements of **multiple data types**, it's efficient to declare the type as “var” and let the compiler decide the type of each element. 


using System;
class varKeyword
{
    static void Main()
    {
      var i=5;
      var j=10;
      Console.WriteLine(i+j);
   }
}

What is the "var" keyword in C#?

Switching type selection to the compiler, "var" in C# helps manage tedious data types and mixed-element arrays, but null variables are invalid.