静态变量实例和应用程序域，发生了什么？ [英] Static Variable Instances and AppDomains, what is happening?

问题描述

我

public static class A
{
   public static string ConnString;
}

[Serializable]
public class Test{
   // Accesing A's field;
   public string ConnString{get{return A.ConnString;}set{A.ConnString=value;}}
}

void Main()
{
   A.ConnString = "InitialString"; // I set A.ConnString in the current domain

   var newDomain = AppDomain.CreateDomain("DomNew");
   Test TObj = newDomain.CreateInstanceAndUnwrap(typeof(Test).Assembly.FullName, typeof(Test).FullName) as Test ;

   TObj.ConnString = "NewDomainString"; // It is supposed to set A.ConnString in the newDomain aka a different instance of A.ConnString

   // Here it is supposed to print two different values
   Console.WriteLine(A.ConnString);  // "InitialString"
   Console.WriteLine(TObj.ConnString); // "NewDomainString"
}

但是，没有！这两个WriteLines，打印出相同的价值NewDomainString！
为什么???

But NO! The two WriteLines, print out the same value "NewDomainString"! WHY???

此代码

TObj.ConnString = "NewDomainString"

应该更改新创建的域字符串，但似乎它们都指的是同一个实例！

is supposed to change the string in the newly created domain, but it seems they both refer to the same instance!

为什么，这里发生了什么？

Why, what is happening here?

推荐答案

有只有两个办法一类是从另一个AppDomain-可接触的是类 [Serializable接口] ，作为你的测试类中，另一种是如果该类从 MarshalByRefObject的继承。因为你的类是序列化的，是每一个跨AppDomain的调用创建它的一个副本。因此，测试主AppDomain中得到，当你调用...

There are only two ways for a class to be accessible from another AppDomain- one is is the class is [Serializable], as your Test class is, the other is if the class inherits from MarshalByRefObject. Because your class is Serializable, a copy of it is created for every cross-AppDomain call. So the Test that the main appdomain gets when you call...

Test TObj = newDomain.CreateInstanceAndUnwrap(typeof(Test).Assembly.FullName, typeof(Test).FullName) as Test;

其实并没有被在DomNew创建AppDomain-是本地的一个副本的测试实例为主的AppDomain，因此，从主的AppDomain引用了静态变量。

is actually not the Test instance that was created in the "DomNew" AppDomain- it is a copy local to the "main" AppDomain, and therefore references the static variables from the "main" AppDomain.

如果你想测试来表现出的行为，你期望的那样，使之从MarshalByRefObject继承的，而不是被序列化。

If you want Test to exhibit the behavior that you expect, make it inherit from MarshalByRefObject instead of being Serializable.

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