传递引用类型对象并更改值 [英] Passing reference type objects and changing the values

问题描述

我正在尝试将引用类型对象传递给方法并从那里更改它。当我更改它时，我没有对传递给方法的变量进行更改。

I am trying to pass reference type object into a method and changing it from there. When I change it I don't have that change on the variable which is passed to method.

以下是示例：

public interface IPerson
{
    string Name { get; }
}

public class Teacher : IPerson
{
    public string Name { get; set; }

    public string LastName { get; set; }
}

//......

public void CreateTeacher(IPerson teacher)
{
    teacher = new Teacher() { Name = "Teacher name", LastName = "Teacher's last name"};
}
//.....

//I am trying this, but after I call CreateTeacher() variable teacher is null
IPerson teacher=null;
CreateTeacher(teacher);
string n = teacher.Name;

运行 CreateTeacher（）变量老师是还是空的？有人可以解释为什么吗
我知道我可以在我的 CreateTeacher（）方法上返回 IPerson 或使用 out ，但我不能使用它们。

After running CreateTeacher() variable teacher is still null? Can anyone explain why? I know I could return IPerson on my CreateTeacher() method or use out, but I can't use them.

IPerson 界面位于不同的dll和教师 class是一个不同的dll。方法 CreateTeacher 与class相同。

The IPerson interface is in a different dll and Teacher class is in a different dll. The method CreateTeacher is the same dll where class is.

更新：

这是我尝试过的其他内容：

Here is something else I tried:

  IPerson teacher=new Teacher();
  CreateTeacher(teacher);
  string n = teacher.Name;//I have the changes here now

  //......

    public void CreateTeacher(IPerson teacher)
    {
        ((Teacher)teacher).Name = "My Name";
    }

第一个例子和第二个例子有什么区别？是因为传递的值是 null ？

What is the difference between 1st example and 2nd? Is it because of the passed value was null?

感谢您的帮助！

推荐答案

除了RedPolygon的答案之外......我觉得这可能会让事情变得清晰。

In addition to RedPolygon's answer.. I feel like this might clear things up.

As解释，您正在更改引用的值..而不是引用指向的对象。

As explained, you're changing the value of the reference.. not the object pointed to by the reference.

将代码更改为：

public interface IPerson {
    string Name { get; set; }
}

public void CreateTeacher(IPerson teacher) {
    teacher.Name = "Teacher name";
}

IPerson teacher = new Teacher();
CreateTeacher(teacher);

..这将有效。为什么？有几个原因。

..that will work. Why? A couple of reasons.

1. 它不再是 null 了，我们 new it up。


2. 你不是 new up在 CreateTeacher 方法中，从而将复制的引用指向一个全新的对象。这意味着你正在改变你的两个引用所指向的对象。

1. It isn't null anymore, we "new it up".
2. You aren't "new'ing it up" in the CreateTeacher method, thereby pointing the copied reference at an entirely new object. This means you're changing the object pointed to by both of your references.

令人困惑......是的，但你明白了你可以玩这样的例子。

It's confusing.. yes, but you understand it when you have a play around with examples like this.

编辑：

我不得不点燃油漆并放我展示了令人敬畏的MSPaint技能：

I had to fire up paint and put my awesome MSPaint skills on display:

这是你的第一个片段流程：

This is your first snippet flow:

这是我的代码段（和你的第二个）一））：

This is my snippet (and your second one):

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