unhandled exception will make WCF service crash?

Question

I want to know whether unhandled exception will make WCF service crash. I have written the following program which shows unhandled exception in a thread started by WCF service will make the whole WCF service crash.

My question is, I want to confirm whether unhandled exception in threads (started by WCF service) will make WCF crash? My confusion is I think WCF should be stable service which should not crash because of unhandled exception.

I am using VSTS 2008 + C# + .Net 3.5 to develop a self-hosted Windows Service based WCF service.

Here are the related parts of code,

namespace Foo
{
    // NOTE: If you change the interface name "IService1" here, you must also update the reference to "IService1" in Web.config.
    [ServiceContract]
    public interface IFoo
    {
        [OperationContract]
        string Submit(string request);
    }
}

namespace Foo
{
    // NOTE: If you change the class name "Service1" here, you must also update the reference to "Service1" in Web.config and in the associated .svc file.
    public class FooImpl : IFoo
    {
        public string Submit(string request)
        {
            return String.Empty;
        }
    }
}

namespace Foo
{
    public partial class Service1 : ServiceBase
    {
        public Service1()
        {
            InitializeComponent();
        }

        ServiceHost host = new ServiceHost(typeof(FooImpl));

        protected override void OnStart(string[] args)
        {
            host.Open();
            // start a thread which will throw unhandled exception
            Thread t = new Thread(Workerjob);
            t.Start();
        }

        protected override void OnStop()
        {
            host.Close();
        }

        public static void Workerjob()
        {
            Thread.Sleep(5000);
            throw new Exception("unhandled");
        }
    }
}

Answer 1

An unhandled exception on the service side will cause the channel (the connection between the client and the server) to "fault" - e.g. to be torn down.

From that point on, you cannot call from the client using the same proxy client object instance anymore - you'll have to re-create the proxy client.

Your best bet is to handle all error on the server side whenever possible. Check out the IErrorHandler interface, which you should implement on your service implementation class, to turn all unhandled .NET exceptions into either SOAP faults (which will NOT cause the channel to fault), or to report / swallow them entirely.

Marc