c# ?? operator

?? Operator

The ?? operator is called the null-coalescing operator and is used to define a default value for a nullable value types as well as reference types. It returns the left-hand operand if it is not null; otherwise it returns the right operand.

class NullCoalesce{    static int? GetNullableInt()    {        return null;    }    static string GetStringValue()    {        return null;    }    static void Main()    {        // ?? operator example.        int? x = null;        // y = x, unless x is null, in which case y = -1.        int y = x ?? -1;        // Assign i to return value of method, unless        // return value is null, in which case assign        // default value of int to i.        int i = GetNullableInt() ?? default(int);        string s = GetStringValue();        // ?? also works with reference types.         // Display contents of s, unless s is null,         // in which case display "Unspecified".        Console.WriteLine(s ?? "Unspecified");    }}