. Net (C #) TPL: Parallel loop and Exception Handling for multiple tasks

Similar to exceptions in for/foreach, any exceptions in the parallel loop end the entire loop, therefore, the entire loop will not be terminated immediately (if a thread is working for a long time and occurs after the throwifcancellationrequested method of cancellationtoken ).

 

Code:

Try

{

Parallel. For (0, 5, (I) =>

{

Throw new exception ("exception. Iterations: "+ I );

});

}

Catch (aggresponexception AE)

{

Foreach (VAR exp in AE. innerexceptions)

Console. writeline (exp. Message );

}

A subset of 0-4 will be output (it may also be all 0-4 output, because all five threads are completed quickly ).

 

Unlike parallel. For and foreach, parallel. InvokeAll tasks are always completed.And then wrap all exceptions in aggresponexception.

Let's look at this Code:

Try

{

Parallel. Invoke () =>{ throw new exception ("1 ");},

() => {Thread. Sleep (1500); throw new exception ("2 ");},

() => {Thread. Sleep (3000); throw new exception ("3 ");});

}

Catch (aggresponexception AE)

{

Foreach (VAR ex in AE. innerexceptions)

Console. writeline (ex. Message );

}

 

 

The result is output:

3

2

1

 

Task. waitall is similar to parallel. Invoke. Any (or multiple) task exception does not affect the execution of any other task.

Try

{

VaR T1 = task. Factory. startnew () =>

{

Thread. Sleep (700 );

Throw new exception ("1 ");

});

 

VaR t2 = task. Factory. startnew () =>

{

Thread. Sleep (1000 );

Throw new exception ("2 ");

});

 

Task. waitall (T1, T2 );

}

Catch (aggresponexception AE)

{

Foreach (VAR exp in AE. innerexceptions)

Console. writeline (exp. Message );

}

 

The output is as follows:

2

1

 

Both exceptions are in the innerexceptions attribute of aggresponexception.

 

For exceptions in task execution (rather than task. waitall), refer to this article:

. Net (C #) TPL: the task is not aware of exceptions and taskscheduler. unobservedtaskexception events.

 

For cancellation exceptions, refer:

. Net (C #) TPL: operationcanceledexception exception after the operation is canceled in task, parallel, and Plinq