[untitled] understand DNET application domain

Application domain

Operating systems and runtime environments often provide some form of isolation between applications . for example ,Windows Use processes to isolate applications . 

The application domain is security 、 reliability 、 Version control and unloading assemblies provide isolation boundaries . Application domains are usually created by the runtime host , The runtime host is responsible for booting the common language runtime before running the application .

The application domain provides a more secure 、 More versatile processing unit , The common language runtime can use this unit to provide isolation between applications . You can have the same isolation level （ Exists in a separate process ） Several application domains run in a single process of , It will not cause additional overhead in terms of interprocess calls or interprocess switches . The ability to run multiple applications in one process significantly enhances the scalability of the server .

The isolation provided by the application domain has the following advantages ：
    Errors in one application will not affect other applications . Because type safe code does not cause memory errors , So using the application domain can ensure that the code running in one domain will not affect other applications in the process .
    It can stop a single application without stopping the whole process . Using application domains allows you to uninstall code that runs in a single application .

Before you can execute the code contained in the assembly , The assembly must be loaded into the application domain . Running a normal application will cause several assemblies to be loaded into an application domain .

There are three options for loading domain neutral assemblies ：
    LoaderOptimization.SingleDomain, LoaderOptimization.MultiDomain, LoaderOptimization.MultiDomainHost;

Make a simple example program ;

using System;
using System.Reflection;

class AppDomain1
{
    public static void Main()
    {
        Console.WriteLine(" Create an application domain ......");
        AppDomain domain = AppDomain.CreateDomain("MyDomain");

        Console.WriteLine("Host domain: " + AppDomain.CurrentDomain.FriendlyName);
        Console.WriteLine("child domain: " + domain.FriendlyName);
        Console.WriteLine("Application base is: " + domain.BaseDirectory);
        Console.WriteLine("Relative search path is: " + domain.RelativeSearchPath);
        Console.WriteLine("Shadow copy files is set to: " + domain.ShadowCopyFiles);
    }
}

    AppDomain.CurrentDomain.FriendlyName, This one is original ;

    domain.FriendlyName, This is created separately ;

    No output 2 Attributes may need to be set first ;