线程中的异常处理，联系WCF服务

Question

I have question in regards to exception handling in threads. I have a simple WCF service which takes some bytes as input. This WCF Service is called from a console application.

Method Snippet(MyMethod)

try 
{
   _service.ImportBytes(bytes);
   _service.Close();

}
catch(Exception e) 
{
   _logger.Error(e.Message);
   _service.Abort();
}

If this is method called directly from the Main thread the exception will occur, since my service is taken down(Stopped the application in IIS).

But if It's calledfrom a thread, the exception will never occur:

 var thread = new Thread(() => MyMethod(file);
 thread.Start()

Since this method should be called several times, in a foreach loop I figured out that if I create one thread for each of the files. If one thread fails, it should just logg it and die, so it doesn't interrupt the application itself.

How should I handle exceptions inside a thread?

Answer 1

In .NET 4.0 the Task Parallel Library (TPL) is added. This is the preferred way to work with threading.

A Task is an object that encapsulates an operation that will return a value at some point or an exception.

The basic idea is that you do something like this:

Task.Run(() => { /* your code */ });

This will return a Task object that finishes when the inner code is finished. You can schedule continuations on such a Task object to run whenever that happens. But since you are executing WCF service calls you can make your life easier by letting Visual Studio generate asynchronous methods for you. Especially since WCF methods are a form of asynchronous I/O and you can consume these without having to wrap them in a thread yourself.

This means that all your methods end with the postfix 'Async' and return a Task object. By using async and await you can easily consume these. By using Task.WhenAll you can let multiple Tasks run in parallel. Task.WhenAll will return a Task in the Faulted state with all the exceptions that where thrown by one of your Tasks when something goes wrong.

Here is some documentation on using async and wait with WCF services that should get you started.