Catching Error when using Task.Factory

Question

i am using the following

Task.Factory.StartNew(() => DoPrintConfigPage(serial)); 

then the function i am calling looks like this

private void DoPrintConfigPage(string serial)  {      //do printing work  } 

My problem is an exception is being thrown inside the thread and not being handled.

I have tried wrapping it in a try catch

try {     Task.Factory.StartNew(() => DoPrintConfigPage(serial)); } catch (Exception ex) { } 

but it still is not catching the error and thus crashing the application.

How can I catch exceptions in the main thread so I can handle them?

Update

I have made the changes recommended below and still it is saying the exception is unhandled

var task =  Task.Factory.StartNew(() => DoPrintConfigPage(serial))                                .ContinueWith(tsk =>                                {                                   MessageBox.Show("something broke");                                },TaskContinuationOptions.OnlyOnFaulted); 

then in my DoConfigPage I added another try catch.

In this catch is now where it is crashing and saying the exception being thrown was unhandled, what am I missing?

private void DoPrintConfigPage(string serial) {     try     {         //call the print function     }     catch (Exception ex)     {         throw ex;   //it is crashing here and saying it is unhandled     } } 

I also tried what Eric J. suggested with the same results

var task = Task.Factory.StartNew(() => DoPrintConfigPage(serial));  try {     task.Wait();                   } catch (AggregateException ex) { MessageBox.Show("something broke"); } 

Answer 1

Alternatively, you can chain your task creation and add a ContinueWith:

var job = Task.Factory     .StartNew(...)     .ContinueWith(tsk =>           {               // check tsk for exception and handle          }); 

EDIT: This snippet, when run, pops up the message box for me:

void Main() {     var serial = "some serial";     var task =  Task.Factory         .StartNew(() => DoPrintConfigPage(serial))         .ContinueWith(tsk =>         {             MessageBox.Show("something broke");             var flattened = tsk.Exception.Flatten();              // NOTE: Don't actually handle exceptions this way, m'kay?             flattened.Handle(ex => { MessageBox.Show("Error:" + ex.Message); return true;});         },TaskContinuationOptions.OnlyOnFaulted);  }  public void DoPrintConfigPage(string serial) {     throw new Exception("BOOM!"); } 

Answer 2

Your try block is exited right after you start the new task, because that method just continues to run.

Instead you can catch the Exception as an AggregateException where you wait for the task (or multiple tasks) to complete:

var task1 = Task.Factory.StartNew(() => {     throw new MyCustomException("I'm bad, but not too bad!"); });  try {     task1.Wait(); } catch (AggregateException ae) {     // Assume we know what's going on with this particular exception.      // Rethrow anything else. AggregateException.Handle provides      // another way to express this. See later example.      foreach (var e in ae.InnerExceptions)     {         if (e is MyCustomException)         {             Console.WriteLine(e.Message);         }         else         {             throw;         }     }  } 

http://msdn.microsoft.com/en-us/library/dd997415.aspx