Question

I know the standard way of using the null coalescing operator in C# is to set default values.

string nobody = null; string somebody = "Bob Saget"; string anybody = "";  anybody = nobody   ?? "Mr. T"; // Returns Mr. T anybody = somebody ?? "Mr. T"; // Returns "Bob Saget" 

But what else can ?? be used for? It doesn’t seem as useful as the ternary operator, apart from being more concise and easier to read than:

nobody = null; anybody = nobody == null ? "Bob Saget" : nobody; // Returns Bob Saget 

So given that fewer even know about null coalescing operator…

• Have you used ?? for something else?

• Is ?? necessary, or should you just use the ternary operator (that most are familiar with)

Answer 1

Well, first of all, it’s much easier to chain than the standard ternary operator:

string anybody = parm1 ?? localDefault ?? globalDefault; 

vs.

string anyboby = (parm1 != null) ? parm1                : ((localDefault != null) ? localDefault                : globalDefault); 

It also works well if a null-possible object isn’t a variable:

string anybody = Parameters["Name"]               ?? Settings["Name"]               ?? GlobalSetting["Name"]; 

vs.

string anybody = (Parameters["Name"] != null ? Parameters["Name"]                  : (Settings["Name"] != null) ? Settings["Name"]                  :  GlobalSetting["Name"];