Question

I’m developing a Silverlight LOB application.
Due to some required functionality I’ve created a new NewBasePage class for all pages. This class is derived from the Page class. I’ve added couple events and raise them manually.

But I’m stuck with some stuff. I need to check whether all methods that are bound to some event were successfully completed. Is there any way to do this?

New Base Class:

public class NewPageBase : Page
{
        public void RefreshData(Action resultAction = null)
        {
            if (StartRefreshingData != null) StartRefreshingData(this, null);

            if (resultAction != null) resultAction();
        }

        public event EventHandler StartRefreshingData;

}

Xaml:

<newbase:NewBasePage ...>

...

  <i:Interraction.Triggers>
    <i:EventTrigger EventName="StartRefreshingData">
        <i:InvokeCommandAction Command="{StaticResource someCommandFromViewModel}"/>
    </i:EventTrigger>
  </i:Interraction.Triggers>
</newbase:NewBasePage>

Answer 1

If you want to know if any event handler failed to do his work you can either throw an Exception or provide a custom EventArgs type which tracks if any event handler failed.

public class FailureEventArgs : EventArgs // not the best name, I know
{
    private bool _failed;

    public bool Failed
    {
        get { return _failed; }
        set { _failed |= value; }
    }
}

Usage:

// Event declaration
public event EventHandler<FailureEventArgs> MyFailingEvent;

// Event invocation
private void Invoke()
{
    bool failure = false;
    var handler = MyFailingEvent;
    if (handler != null)
    {
        var args = new FailureEventArgs();
        handler(this, args);
        failure = args.Failed;
    }

    // more code, aware of possible failure
}

// In your event handler
private void OnEvent(object sender, FailureEventArgs args)
{
    var errorOccured = false;

    // some code which could set errorOccured to true

    args.Failure = errorOccured;
}

And, as already mentioned in my comment above, once the invokation of the event is over, you can be sure that there is no attached event handler processed anymore.