第22章 CLR寄宿和AppDomain

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Runtime.Remoting;
using System.Threading;

public sealed class Program
{
    public static void Main()
    {
        Marshalling();
    }

    private static void Marshalling()
    {
        // Get a reference to the AppDomain that that calling thread is executing in
        //获取AppDomain的一个引用
        AppDomain adCallingThreadDomain = Thread.GetDomain();

        // Every AppDomain is assigned a friendly string name (helpful for debugging)
        //每个AppDomain都被赋予了一个友好字符串名称
        // Get this AppDomain‘s friendly string name and display it
        String callingDomainName = adCallingThreadDomain.FriendlyName;
        Console.WriteLine("Default AppDomain‘s friendly name={0}", callingDomainName);

        // Get & display the assembly in our AppDomain that contains the ‘Main‘ method
        //获取AppDomain中包含了“Main”方法的程序集
        String exeAssembly = Assembly.GetEntryAssembly().FullName;
        Console.WriteLine("Main assembly={0}", exeAssembly);

        // Define a local variable that can refer to an AppDomain
        //定义一个局部变量来引用一个AppDomain
        AppDomain ad2 = null;

        // *** DEMO 1: Cross-AppDomain Communication using Marshal-by-Reference
        //使用“按引用封送”进行跨AppDomain通信
        Console.WriteLine("{0}Demo #1", Environment.NewLine);
        // Create new AppDomain (security & configuration match current AppDomain)
        ad2 = AppDomain.CreateDomain("AD #2", null, null);
        MarshalByRefType mbrt = null;
        // Load our assembly into the new AppDomain, construct an object, marshal 
        //将我们的程序集加载到新AppDomain中，构造一个对象，把它封送回我们的AppDomain
        // it back to our AD (we really get a reference to a proxy)
        mbrt = (MarshalByRefType)
           ad2.CreateInstanceAndUnwrap(exeAssembly, "MarshalByRefType");
        Console.WriteLine("Type={0}", mbrt.GetType());  // The CLR lies about the type
        // Prove that we got a reference to a proxy object
        Console.WriteLine("Is proxy={0}", RemotingServices.IsTransparentProxy(mbrt));
        // This looks like we‘re calling a method on MarshalByRefType but, we‘re not.
        // We‘re calling a method on the proxy type. The proxy transitions the thread
        // to the AppDomain owning the object and calls this method on the real object.
        mbrt.SomeMethod();
        // Unload the new AppDomain
        //卸载新的AppDomain
        AppDomain.Unload(ad2);
        // mbrt refers to a valid proxy object; the proxy object refers to an invalid AppDomain
        try
        {
            // We‘re calling a method on the proxy type. The AD is invalid, exception is thrown
            mbrt.SomeMethod();
            Console.WriteLine("Successful call.");
        }
        catch (AppDomainUnloadedException)
        {
            Console.WriteLine("Failed call.");
        }

        // *** DEMO 2: Cross-AppDomain Communication using Marshal-by-Value
        Console.WriteLine("{0}Demo #2", Environment.NewLine);
        // Create new AppDomain (security & configuration match current AppDomain)
        ad2 = AppDomain.CreateDomain("AD #2", null, null);
        // Load our assembly into the new AppDomain, construct an object, marshal 
        // it back to our AD (we really get a reference to a proxy)
        MarshalByValType mbvt = (MarshalByValType)
           ad2.CreateInstanceAndUnwrap(exeAssembly, "MarshalByValType");
        // Prove that we did NOT get a reference to a proxy object
        Console.WriteLine("Is proxy={0}", RemotingServices.IsTransparentProxy(mbvt));
        // This looks like we‘re calling a method on MarshalByValType and we are.
        Console.WriteLine("Returned object created " + mbvt.ToString());
        // Unload the new AppDomain
        AppDomain.Unload(ad2);
        // mbvt refers to valid object; unloading the AppDomain has no impact.
        try
        {
            // We‘re calling a method on an object; no exception is thrown
            Console.WriteLine("Returned object created " + mbvt.ToString());
            Console.WriteLine("Successful call.");
        }
        catch (AppDomainUnloadedException)
        {
            Console.WriteLine("Failed call.");
        }

        // DEMO 3: Cross-AppDomain Communication using non-marshalable type
        Console.WriteLine("{0}Demo #3", Environment.NewLine);
        // Create new AppDomain (security & configuration match current AppDomain)
        ad2 = AppDomain.CreateDomain("AD #2", null, null);
        // Load our assembly into the new AppDomain, construct an object, marshal 
        // The object‘s method returns an non-marshalable object; exception
        NonMarshalableType nmt = (NonMarshalableType)
           ad2.CreateInstanceAndUnwrap(exeAssembly, "NonMarshalableType");
        // The object‘s method returns an non-marshalable object; exception
    }
}

// Instances can be marshaled-by-reference across AppDomain boundaries
public sealed class MarshalByRefType : MarshalByRefObject
{
    public MarshalByRefType()
    {
        Console.WriteLine("{0} ctor running in {1}",
           this.GetType().ToString(), Thread.GetDomain().FriendlyName);
    }

    public void SomeMethod()
    {
        Console.WriteLine("Executing in " + Thread.GetDomain().FriendlyName);
    }
}

// Instances can be marshaled-by-value across AppDomain boundaries
[Serializable]
public sealed class MarshalByValType : Object
{
    private DateTime m_creationTime = DateTime.Now; // NOTE: DateTime is [Serializable]

    public MarshalByValType()
    {
        Console.WriteLine("{0} ctor running in {1}, Created on {2:D}",
           this.GetType().ToString(),
           Thread.GetDomain().FriendlyName,
           m_creationTime);
    }

    public override String ToString()
    {
        return m_creationTime.ToLongDateString();
    }
}

// Instances cannot be marshaled across AppDomain boundaries
// [Serializable]
public sealed class NonMarshalableType : Object
{
    public NonMarshalableType()
    {
        Console.WriteLine("Executing in " + Thread.GetDomain().FriendlyName);
    }
}