CSLA 3.0 Beta 1 WPF ValidationPanel Recursive Infinite Loop?

GlennMiller posted on Wednesday, June 13, 2007

We're using WPF, and seem to have found a problem with the CSLA validation panel causing an infinite loop. Here's the scenario:

We have a details view where at run-time we build a list of text boxes representing properties of a business object selected from a list in separate "sidebar" view. The run-time code binds the text boxes to the selected BO's properties. We keep the underlying details view reference around for the remaining scope of our application. As the user clicks different BO's in the sidebar, we rebind the details view. The BO's are not all of the same type, so we rebind by removing the text boxes and recreating a new set of them.

In the details view we use CSLA's validation panel to wrap around the dynamically added bound text boxes.  We added the Validation panel beforehand in XAML, and the run-time code adds the text boxes to it.

The first time a user selects an item in the sidebar things work fine (i.e. you select an item and the bindings are added and the details view shows the bound controls and validation works fine). However, subsequent clicks on the sidebar make the application crash, caused by an infinite loop in the validation panel logic.

Here is where our stack-trace shows a recursive infinite loop. It happens in our rebinding code, after we've removed the text boxes for the first BO and before we've added them for the second.

ReloadBindings() is called, which calls _bindings.Clear(); base.FindChildBindings(); and  Refresh();.

 In  Refresh();  ErrorScan(); is called.

 ErrorScan is where things go wrong:

if (_bindings.Count == 0)
    ReloadBindings();

We are back up to ReloadBindings, and the program loops.

We were able to stop this behavior by putting a check in ReloadBindings to not call Refresh unless _bindings.Count is greater than zero.

From what we can tell it was assumed that when ReloadBindings was called there would always be bound controls within the CSLA Validation panel? Is this a correct assertion? Or is this a bug that can be simply fixed by putting in that greater than zero check?

Paul Czywczynski replied on Wednesday, June 13, 2007

I believe the latest source tree has the fix. We came across it a few weeks ago and Rocky was able to check in a fix for us. We've hadn't the problem since. You could wait until beta 2 which I think will be ready soon.