Exception with INotifyLocationChanged

[Etienne]

Hi,

I use INotifyLocationChanged to raise event when items of a VisualizationLayer move and it throws an exception in some particular case. I've joined a sample project that demonstrate this particular case. I'm I doing something wrong or this is a bug ?

Thank you,

Etienne

[Martin Ivanov]

Hi Etienne,

The reported error is caused by the fact that the LocationChanged event is raised for elements that are not added in the VisualizationLayer. In your case the layer with the zones always has two objects, however, the MoveForward command is changing the Location of all zones of all elements which throws an exception in the layer's code.

In order to prevent the error you will need to ensure that the LocationChanged event in your viewmodel is raised only if the model is added in the layer.

I hope this information is useful.

Regards,
Martin
Telerik

[Etienne]

Hi Martin,

Thanks for your reply, but I'm not sure how I can do this elegantly. I would have expected that when an item is removed from a layer, the layer unsubscribe from the LocationChanged event or at least ignore future event.

Regards,

Etienne

[Martin Ivanov]

Hi Etienne,

Since the event handler is manually attached you will need also to manually remove it from the object. However, we will take some time to investigate the observed behavior in the VisualizationLayer's code too. 

As for avoiding the exception, you can use different approaches based on your application's requirements. I updated your project to demonstrated a possible implementation which you can use. Basically, I defined a Boolean property in the MapItemViewModel that tells if the item has a parent (is it attached somehow to the layer) or not. Then, I am using the property in the condition for raising the LocationChanged event. I made few changes in the following files to set the property when the SelectedThing is changed and when the Things collection is populated:

• MapItemViewModel.cs
• ViewModel.cs

I commented the changed parts of the code. Please give the project a try and let me know if this approach works for you.

Regards,
Martin
Telerik

[Etienne]

Hi Martin,

Is there any update on your side about this ?

Regards,

Etienne

[Martin Ivanov]

Hello Etienne,

We investigate this and found out this is an issue in RadMap which we logged in our feedback portal. If you follow the item you will be notified as soon as there is any change in its status. We also updated your Telerik points as a small gesture of gratitude for reporting this to us.

Regards,
Martin
Telerik