问题描述

我知道在 C# 中使用 null 合并运算符的标准方法是设置默认值值.

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"

但是??还能用来做什么?除了更简洁和更容易阅读:

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

因此，很少有人知道空合并运算符...

So given that fewer even know about null coalescing operator...

• 您是否将 ?? 用于其他用途?

?? 是必需的，还是应该使用三元运算符(即大多数都熟悉)

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

推荐答案

嗯，首先，它比标准的三元运算符更容易链接:

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

string anybody = parm1 ?? localDefault ?? globalDefault;

对比

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

如果可能为 null 的对象不是变量，它也能很好地工作:

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

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

对比

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

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