C＃传值/ REF？ [英] C# pass by value/ref?

问题描述

常见的问题，但我可以用一个英语的解释..

Common question but I could use an "english" explanation..

北京时间它像Java，其中

Ist it like Java where

Cat myCat

实际上是一个指向猫？

actually is a pointer to Cat?

如果我真的在C＃创建拷贝构造函数？

Should I really create copy constructors in c#?

据我所知，我们按值传递，但现在我的问题是，我们是路过的指针的值或对象的完整副本？

I understand we are passing by value, but now my question is are we passing by pointer value or full copy of the object?

如果是后者，心不是太贵了性能/内存明智？就是当你必须使用ref关键字？

if its the latter, isnt that too expensive performance/memory wise? Is that when you have to use the ref keyword?

推荐答案

由于@rstevens回答，如果它是一个类，myCat是一个参考。但是，如果你传递myCat一个方法调用，然后引用本身是按值传递 - 即参数本身会引用同一个对象，但它是一个完全新的参考，因此，如果您指定为null，或创建一个新的对象，老myCat参考仍将指向原始对象。

As @rstevens answered, if it is a class, myCat is a reference. But if you pass myCat to a method call, then the reference itself is passed by value - i.e. the parameter itself will reference the same object, but it's a completely new reference, so if you assign it to null, or create a new object, the old myCat reference will still point to the original object.

SomeMethod(myCat);

void SomeMethod(Cat cat)
{
    cat.Miau(); //will make the original myCat object to miau
    cat = null; //only cat is set to null, myCat still points to the original object
}

乔恩斯基特大约有一个好文章。

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