Just the other day I came across a C# operator that I found particularly useful and decided to share it with everyone here at SOTC - the ?? operator. The briefest explanation is this: ?? is used a lot like the conditional operator (?:), except instead of any condition, it will only check if the value on the left is null. If it is not null, it returns the item on the left - otherwise it will return the thing on the right.
We'll start with a really simple example - reference types:
string myOtherString = myString ?? "Something Else";
Console.WriteLine(myOtherString);
//Output: "Something Else"
Here we can see a string being assigned to null. Next we use the ?? operator to assign a value to myOtherString. Since myString is null, the ?? operator assigns the value "Something Else" to the string.
Let's get a little more complicated and see an example using nullable types.
int anotherInt = myInt ?? 1234;
Console.WriteLine(anotherInt.ToString());
//Output: "1234"
The ?? operator is a great way to assign a nullable type to a non-nullable type. If you were to attempt to assign myInt to anotherInt, you'd receive a compile error. You could cast myInt to an integer, but if it was null, you'd receive a runtime exception.
Granted, you can do the exact same thing with the regular conditional operator:
int anotherInt = myInt.HasValue ? myInt.Value : 1234;
Console.WriteLine(anotherInt.ToString());
//Output: "1234"
But, hey, that's a whole 22 extra characters - and really, it does add up when you are doing a lot of conversions from nullable to non-nullable types.
If you'd like to learn more about C# operators, I'd recommend checking out our two-parter series on operator overloading (part1, part2).
10/10/2008 - 08:50
Thanks for the post. This is a very handy feature that I've gotten in the habit of using.. it works especially well in templates where readability is a concern.