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To my knowledge perhaps the least used operator in C# is the null-coalescing operator .

But you can use it effectively to reduce the lines of code you write .

The null-coalesce operator can be used to define / return a default value for a nullable value type / reference type and this is represented by two consecutive question marks (??).

Here is how you can use it :

Ex. 1 : Assign default value to Value type

// define a nullable int
int? x = null;

// assign a value to another integer, but check if it contains null value
// if a null is there, assign a default value
int y = x ?? -1;

Ex. 2 : Passing as parameter

public class MyClass
{
// define members here
}

public class TestClass
{
  public void VerifyObject(MyClass myClassObject)
  {
   if (myClassObject == null)
   {
    // display error message
   }
   else
   {
    // do something
   }
  }

  public void Test()
  {
   MyClass myClassObject1 = null;
   MyClass myClassObject2 = new MyClass();

VerifyObject(myClassObject1 ?? myClassObject2);
}
}

Ex. 3 : Create new Object

MyClass myClassObject1 = null;

/*
  instead of writing -
  if (myClassObject1 != null)
  {
   myClassObject2 = myClassObject1;
  }
  else
  {
   myClassObject2 = new MyClass();
  }

Write in a single statement
*/

MyClass myClassObject2 = myClassObject1 ?? new MyClass();

Ex. 4 : Return value from function

/* instead of writing -

if (myClassObject1 != null)
return myClassObject1;

if (myClassObject2 != null)
return myClassObject2;

return null;

Write in a single statement
*/

return myClassObject1 ?? myClassObject2

As the above examples show using null-coalescing operator can help us reduce the lines of code significantly.

Related Tags:
C#, .NET, Null-Coalescing Operator

Author: Rabinarayan Biswal

C#

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