为什么不能我重载+ =运算符在C＃中？但我仍然可以使用它？ [英] Why cant i overload the += operator in C#? But i still can use it?
问题描述
可能重复：
<一href="http://stackoverflow.com/questions/2869245/simple-way-to-overload-compound-assignment-operator-in-c">Simple办法在C＃中重载复合赋值操作符？
我用事件玩弄，并认为事件是怪异。为什么想不出我只是实现他们在一个泛型类。于是，我就发现，我不能过载+ =。 从这里发现语言规范
I was playing around with events and thought events are weird. Why couldnt i just implement them in a generic class. So i tried to and found that i CANT OVERLOAD +=. From the language specs found here
The overloadable unary operators are:
+ - ! ~ ++ -- true false
The overloadable binary operators are:
+ - * / % & | ^ << >> == != > < >= <=
+ =没有列出。现在，在你说世界上没有理由超载+ =我想弹出事实上C＃有事件，它使用+ =运算符和事实，我试图实现事件的乐趣和希望使用+ =运算符。现在，我有一种感觉，有人会说，这就是为什么事件的存在，因为它是唯一的原因。不过，我想提出你可以使用+ =用的时间跨度结构。去试试吧， VAR TS =新的时间跨度（）; TS + = TS; 编译和运行
我看了看时间跨度定义，我不知道它是如何允许它。我看到了一个公共静态时间跨度运营商+（时间跨度T）; 这看起来很奇怪，但是后来我意识到它的东西，像 VAR名称= + TS; 喜欢你如何能做到 VAR名称= -TS; 为否定
I looked at TimeSpan definition and i have no idea how it is allowing it. I saw a public static TimeSpan operator +(TimeSpan t); which looked suspicious but then i realize its for something like var name = +ts; like how you can do var name = -ts; for negation.
所以我的问题是，我该如何使用+ =我的结构或类。这似乎是支持我只是不能似乎找到它的文档。
So my question is, how do i use the += for my struct or class. It appears to be supported i just cant seem to find the documentation on it.
推荐答案
事件不超载 + = 和 = - 运营商。这只是很难codeD在C＃编译器它转换成的添加/删除事件的方法。
Events don't overload the += and -= operator. This is just hardcoded in the C# compiler which translates it into the add/remove methods of that event.
您只能超负荷 + 和 - 然后间接超载 + = 和 = - 。如果你重载 + 然后自动 X + = Y 过载到 X = X + Y 。因此，对于你的类型，你不需要投入任何额外的工作。只要超载 + ，你会得到 + = 免费。当然，这需要在左侧的参数和结果类型是兼容的，但是这是通常情况下。
You can only overload + and - which then indirectly overload += and -=. If you overload + then automatically x += y becomes overloaded to x = x + y. So for your type you don't need to put in any extra work. Just overload + and you'll get += for free. This of course requires the left side argument and the result type being compatible, but that's usually the case.
这是你不能重载的原因 + = 分别是最有可能的，它创建奇怪的语义引用类型。如果 + = 修改的左侧则现有实例以下code会表现得出奇：
The reason that you can't overload += separately is most likely that it creates strange semantics for reference types. If += modified the existing instance of the left side then the following code would behave strangely:
MyClass x=new MyClass();
MyClass y=x;
x+=SomeThing;
y has changed now too
在另一方面与 + = 意 X = X + Y 这code创建一个新的例如，它分配到x。而原始实例保持不变y中;
On the other hand with += meaning x = x+y this code creates a new instance which it assigns to x. And the original instance remains unmodified in y;
在C ++中，另一方面，可以安全地指定 + = 单独的过载，因为你可以重载赋值和拷贝构造函数在同一时间和使用，要得到正确的语义。
In C++ on the other hand it is possible to safely specify a separate overload for += because you can overload the assignment and copy-constructor at the same time and use that to get the correct semantics.
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