What is ' ?? ' operator ?

 Posted by Ddd on 1/26/2011 | Category: C# Interview questions | Views: 2675 | Points: 40

It is also called as the null coalescing operator.
It evaluates which value will be assigned to a variable of a particular type if we have 2 variables
of a particular type(nullable or a reference type).

The 1st input variable must be a nullable or a reference type.
The 2nd input variable should be of the same type as the first one or of a type that can be implicitly
converted to the type of the first variable.

input 1 input 2 target
null not null value of 2nd input
not null null value of 1st input
not null not null value of 1st input
null null null
class Class2
static void Main()
int? a = null;
int b;
int c=30;

b=a ?? c;
//b is 30 as a is null
a = 35;
b = a ?? c;
//b is 35 as a is now assigned 35 value


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