CODEWITHSUNDEEP
wcfexceptiontask-parallel-library
Faraaz
Faraaz

Reputation: 137

Exception handling on Tasks without Wait()

What is the best approach to handle exception of a Task that does not Wait()? I read a couple of blogs which spoke about using ContinueWith because regular try/catch cannot handle Task exception. Below code does not validate that.

Method 1:

public class Service1 : IService1
{
    public string GetData(int value)
    {
        var a = Task.Factory.StartNew(ThrowException);
        return string.Format("You entered: {0}", value);
    }


    private void ThrowException()
    {
        try
        {

            Thread.Sleep(6000);
            throw new ArgumentException("Hello from exception");
        }
        catch (Exception)
        {
            Trace.WriteLine("Log it");
        }

    }
}

Method 2:

public class Service1 : IService1
{
    public string GetData(int value)
    {
        var a = Task.Factory.StartNew(ThrowException);
        a.ContinueWith(c => { Trace.WriteLine("Log it"); }, 
TaskContinuationOptions.OnlyOnFaulted);
        return string.Format("You entered: {0}", value);
    }


    private void ThrowException()
    {

            Thread.Sleep(6000);
            throw new ArgumentException("Hello from exception");

    }
}

Are Method 1 and Method 2 doing the same thing? Is there a better way to implement this.

Edit: Added code snippet for continuewith.

Upvotes: 2

Views: 88

Answers (2)

usr
usr

Reputation: 171178

Both methods work and they are equivalent. Choose what you like most. The continuation based one has the advantage that you can make the error handling into an extension method (or some other central helper).

Are you aware that IIS worker processes can suddenly disappear for many reasons? In that case background work is lost. Or, the work faults but the error handler disappears.

Upvotes: 2

Josh Heitz
Josh Heitz

Reputation: 68

It looks like it will work if all you need is to call methods on the Trace class. However, if you need custom exception handling, I would recommend injecting an exception handler:

private void ThrowException(Action<Exception> handleExceptionDelegate)
{
    try
    {
        // do stuff that may throw an exception
    }
    catch (Exception ex)
    {
        if (handler != null)
            handleExceptionDelegate(ex);
    }
}

Then you could do

Task.Factory.StartNew(() =>
{
    ThrowException((ex) =>
    {
        // Handle Exception
    });
});

Upvotes: 1

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