在C＃中引用类型 [英] Reference type in C#

问题描述

考虑这个code：

public class Program
{
    private static void Main(string[] args)
    {
        var person1 = new Person { Name = "Test" };
        Console.WriteLine(person1.Name);

        Person person2 = person1;
        person2.Name = "Shahrooz";
        Console.WriteLine(person1.Name); //Output: Shahrooz
        person2 = null;
        Console.WriteLine(person1.Name); //Output: Shahrooz
    }
}

public class Person
{
    public string Name { get; set; }
}

显然，分配当 PERSON1 到 PERSON2 和名称属性 PERSON2 改变时，名称 PERSON1 也将改变。 PERSON1 和 PERSON2 具有相同的参考。

Obviously, when assigning person1 to person2 and the Name property of person2 is changed, the Name of person1 will also be changed. person1 and person2 have the same reference.

为什么当 PERSON2 = NULL 的 PERSON1 变量不能为空要么？

Why is it that when person2 = null, the person1 variable will not be null either?

推荐答案

两个人和 PERSON2 是引用的，同一个对象。但这些都是不同的参考。所以，当你运行

Both person and person2 are references, to the same object. But these are different references. So when you are running

person2 = null;

正在改变仅供参考 PERSON2 ，剩下参考人和相应的对象不变。

you are changing only reference person2, leaving reference person and the corresponding object unchanged.

我想解释这一点的最好方法是用一个简单的例子。这里是如何的情况看起来像的在的 PERSON2 = NULL ：

I guess the best way to explain this is with a simplified illustration. Here is how the situation looked like before person2 = null:

这里是画面的在的空分配：

And here is the picture after the null assignment:

正如你所看到的，在第二张图片 PERSON2 引用什么（或空，严格来说，由于参考不信邪，参照空是不同的条件，请参见注释通过符文FS ），而人仍然引用现有的对象。

As you can see, on the second picture person2 references nothing (or null, strictly speaking, since reference nothing and reference to null are different conditions, see comment by Rune FS), while person still references an existing object.

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