Start WCF service in a new AppDomain to enable shadow copy (Windows Service hosted)

Question

I have a WCF service library (MyWCFService), which uses MEF to load plugins and hosted by Windows services (All .NET 4.0). I am now trying to run it in a new AppDomain and to enable ShadowCopyFiles in a hope that I can update plugins in the runtime. Here is the code in the Windows service project.

Program.cs

 static class Program
    {  
        static void Main()
        {  
            ServiceBase[] ServicesToRun;
            ServicesToRun = new ServiceBase[] 
            { 
               new MyService() 
            };
            ServiceBase.Run(ServicesToRun);
        }
    }

MyService.cs

  public partial class MyService: ServiceBase
    {
        internal static ServiceHost MyServiceHost = null;
        public MyService()
        {
             // this works but is deprecated..
             AppDomain.CurrentDomain.SetShadowCopyFiles();

            //this is not working.. DLLs still get locked. Require for a new AppDomain
            //AppDomain.CurrentDomain.SetupInformation.ShadowCopyFiles = "true";  

            InitializeComponent();
        }   

        protected override void OnStart(string[] args)
        {
            if(MyServiceHost  !=null)
            {
                MyServiceHost.Close();
            }
            try
            {
                MyServiceHost= new ServiceHost(typeof(MyWCFService));         
                MyServiceHost.Open();
            }
            catch(Exception)
            {
            }          
        }

        protected override void OnStop()
        {
            if (MyServiceHost!= null)
            {
                MyServiceHost.Close();
                MyServiceHost= null;
            }
        }       
    }

Is there any way of doing it? I have done a lot of search, but still don't know how to make it work with my current settings (or I just can't understand...)

I have tried to create a new AppDomain inside Main() and used domain.DoCallBack(new CrossAppDomainDelegate(() => { ServiceBase.Run(ServicesToRun); })) to start the service but I can't start it and keep getting "Error 1053: The service did not respond to the start or control request in a timely fashion".

And then I tried to just enable Shadow copy for the current appdomain by setting AppDomain.CurrentDomain.SetupInformation.ShadowCopyFiles = "true"; in MyWCFService.cs just before InitializeComponent(); I can start the service but the dlls are still locked. however, if I use AppDomain.CurrentDomain.SetShadowCopyFiles(); (a deprecated method) to enable the shadow copy, everything works. I'm more confused.

score 1 · Accepted Answer · answered Jun 26 '14 at 08:45

OK, I ended up with creating a shell/proxy class inherited from MarshalByRefObject and start the service from there, and here is the code:

ServiceShell.cs

public class ServiceShell:MarshalByRefObject
{
     internal static ServiceHost MyServiceHost = null;

     public void Run()
     {
         if (MyServiceHost != null)
         {
             MyServiceHost.Close();
         }
         try
         {
             MyServiceHost = new ServiceHost(typeof(MyWCFService));
             MyServiceHost.Open();
         }
         catch (Exception)
         {
         }          
     }

     public void Stop()
     {
         if (MyServiceHost!= null)
         {
             MyServiceHost.Close();
             MyServiceHost = null;
         }
     }
}

MyService.cs

public partial class MyService: ServiceBase
{        
    AppDomain domain;
    ServiceShell runner;

    public MyService()
    {   
        var setup = new AppDomainSetup
        {
            ShadowCopyFiles = "true"
        };
        domain = AppDomain.CreateDomain("MyServiceHostDomain", AppDomain.CurrentDomain.Evidence, setup);

        runner = (ServiceShell)domain.CreateInstanceAndUnwrap
            (typeof(ServiceShell).Assembly.FullName, typeof(ServiceShell).FullName);
        InitializeComponent();

    }

    protected override void OnStart(string[] args)
    {          
        runner.Run();
    }

    protected override void OnStop()
    {
        runner.Stop();
        AppDomain.Unload(domain);
    }       
}

I'm using the exact pattern, but getting `ThreadAbortException` on `Unload`. furthermore, `Thread.ResetAbort()`, does nothing, so the whole thing crashes. — itsho, Mar 11 '15 at 07:06
@itsho, I think that is the expected result: *The threads in domain are terminated using the Abort method, which throws a ThreadAbortException in the thread.* [AppDomain.Unload Method](https://msdn.microsoft.com/en-us/library/system.appdomain.unload%28v=vs.110%29.aspx) — Bolu, Mar 11 '15 at 12:02

Start WCF service in a new AppDomain to enable shadow copy (Windows Service hosted)

1 Answers1