空合并运算符使用不当？
myFoo = myFoo ?? new Foo();
而不是
if (myFoo == null) myFoo = new Foo();
我认为第一行代码将始终执行分配的想法是否正确？另外，这是空合并运算符的错误使用吗？
myFoo = myFoo ?? new Foo();
instead of
if (myFoo == null) myFoo = new Foo();
Am I correct in thinking that the first line of code will always perform an assignment? Also, is this a bad use of the null-coalescing operator?
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我比较了生成代码的 CIL（确保进行发布构建 - 在项目属性中选中优化代码，这对应于
csc.exe上的/optimize开关>）。这就是我得到的（使用 VS 2008 - 请注意Foo.MaybeFoo()是一种有时返回null，有时返回Foo的方法）GetFooWithIf：GetFooWithCoalescingOperator：因此，除了额外的栈顶复制和弹出之外，其他都是相同的。如果这可以带来可衡量的性能差异，我会专门购买一顶帽子来吃它；因此，选择您认为可读性更好的那个。
（编辑）哦，JITter 可能足够聪明，甚至可以消除这种差异！
I compared the CIL of the generated code (making sure to do a Release build - with Optimize Code checked in the Project Properties, which corresponds to the
/optimizeswitch oncsc.exe). This is what I got (using VS 2008 - note thatFoo.MaybeFoo()is a method that sometimes returnsnull, sometimes aFoo)GetFooWithIf:GetFooWithCoalescingOperator:Thus, the same except for an extra top-of-stack-duplication and pop. If this can be made to make a measurable performance difference, I will purchase a hat specifically for the purpose of eating it; therefore, go with the one that you feel offers better readability.
(edit) oh, and the JITter might be clever enough to get rid of even that difference!
我不认为这是对空合并运算符的错误使用。阅读代码时，尽量简短、简洁，代码的意图很明显。
使用这样的空合并运算符是正确的，您总是会得到一个赋值，但我不会担心这一点。 （如果事实证明它确实是性能问题，那么您已经知道如何解决它）。
I don't think this a bad use of the null-coalescing operator. When reading the code, it is as short and concise as possible, and the intent of the code is obvious.
It is correct that using the null-coalescing operator like this, you will always get an assignment, but I would not worry about that. (And if it really turns out to be a performance issue, you already know how to fix it).
你是正确的，第一行总是会进行分配。除非代码经常执行，否则我不会担心这一点。
You are correct in that the first line will always make an assignment. I would not worry about that unless the code is executed very often.