Jonathan Yong

C# 2.0 introduce a new operator "??". Make no mistake, it is a double question mark.

This operator evaluate an expression and return the value of the expression if not null, else return a default value.

a ?? "default" is equivalent to :


if(a == null)
return "default";
else
return a;


Try the following example:

static void Main(string[] args)
{
    string aa = "abcd";
  
   // This will print "abcd".
   Console.WriteLine("aa is {0}", aa ?? "default text");
  
   aa = null;
   // This will print "default text".
   Console.WriteLine("aa is {0}", aa ?? "default text");  
} 

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Labels: csharp