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Unique ways to use the null coalescing operator [closed] Ask Question

tag-icon • tag-icon c# coding-style null conditional-operator null-coalescing-operator
Unique ways to use the null coalescing operator [closed] Ask 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)

ベストアンサー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"];

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