Exceptions debugging with async and UWP

Question

I'm working on the UWP application. And I'm using async/await a lot. Always when an exception occurs in my code the debugger set break in App.g.i.cs

#if DEBUG && !DISABLE_XAML_GENERATED_BREAK_ON_UNHANDLED_EXCEPTION
            UnhandledException += (sender, e) =>
            {
                if (global::System.Diagnostics.Debugger.IsAttached) global::System.Diagnostics.Debugger.Break();
            };
#endif

But I want to see the line when the exception occured. How to achieve that behavior ?

You would have to handle the exception where it is thrown. For instance a try catch? Not sure what answer you are looking for here — default
– default, Commented May 20, 2016 at 14:33
@Default, the problem is I don't know where it is thrown and I want debuger to show it for me )) — IL_Agent
– IL_Agent, Commented May 20, 2016 at 15:30
@Janak, no, NullReferenceException for examle, in a view model — IL_Agent
– IL_Agent, Commented May 20, 2016 at 15:30
Possible duplicate of Visual Studio: How to break on handled exceptions? — default
– default, Commented May 20, 2016 at 16:04

Petter Hesselberg · Accepted Answer · 2016-05-20 14:48:12Z

9

Add the following method to your App class:

private static void UnhandledError(object sender, UnhandledErrorDetectedEventArgs eventArgs)
{
    try
    {
        // A breakpoint here is generally uninformative
        eventArgs.UnhandledError.Propagate();
    }
    catch (Exception e)
    {
        // Set a breakpoint here:
        Debug.WriteLine("Error: {0}", e);
        throw;
    }
}

In your App constructor:

public UnitTestApp()
{
    CoreApplication.UnhandledErrorDetected += UnhandledError;

    // ...and any other initialization.
    // The InitializeComponent call just sets up error handlers,
    // and you can probably do without in the case of the App class.

    // This can be useful for debugging XAML:
    DebugSettings.IsBindingTracingEnabled = true;
    DebugSettings.BindingFailed +=
        (sender, args) => Debug.WriteLine(args.Message);

}

There are still cases where you don't get a good stack trace, but this is often helpful.

Another approach is to break when an exception is thrown (via Debug, Windows, Exception Settings).

edited May 20, 2016 at 14:48

answered May 20, 2016 at 14:39

Petter Hesselberg

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3 Comments

IL_Agent Over a year ago

Thank you, it's very usefull ! But why debugger can't set break to expected line ?

Petter Hesselberg Over a year ago

Tell Visual Studio to break when (all or any specific) exception is thrown. The stack trace will provide the method, but not thw line.

IL_Agent Over a year ago

Yes ! I've checked all Common Language Runtime Exceptions and not it's working ! Thank you.

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