I tried the sample snippet you referred to above and did notice an issue with the sample. If you look at the "private void GetMapMembers(MapView mapView)" method, you can see that this method is always running on the thread it is called from. Unfortunately, when the 'query definition' custom dockpane is open and a new featureclass or table is added to the current map, this method is called from a background thread which in turn is throwing an exception. So to correct this i made the following changes to the sample:
private void GetMapMembers(MapView mapView)
{
RunOnUiThread(() =>
{
MapMembers.Clear();
if (mapView != null)
{
var tocLayers = mapView.Map.GetLayersAsFlattenedList().OfType<BasicFeatureLayer>().ToList();
var tocTables = mapView.Map.StandaloneTables.ToList();
if (tocLayers.Count > 0 || tocTables.Count > 0)
{
tocLayers.ForEach(x => _mapMembers.Add(x));
tocTables.ForEach(t => _mapMembers.Add(t));
var selectedMapMember = GetSelectedMapMemberInTOC();
if (selectedMapMember != null) //mapmember has been selected
SelectedMapMember = selectedMapMember; //Show that map member's filters
else
SelectedMapMember = MapMembers[0]; //default. Nothing selected in TOC
}
//If no feature layers, show empty dockpanes(DockpaneVisibility)
DockpaneVisibility = MapMembers.Count == 0 ? Visibility.Hidden : Visibility.Visible;
}
});
}
And here are the supporting functions:
#region Threading Utilities
/// <summary>
/// utility function to enable an action to run on the UI thread (if not already)
/// </summary>
/// <param name="action">the action to execute</param>
/// <returns></returns>
internal static Task RunOnUiThread(Action action)
{
if (OnUIThread)
{
action();
return Task.FromResult(0);
}
else
return Task.Factory.StartNew(action, System.Threading.CancellationToken.None, TaskCreationOptions.None, QueuedTask.UIScheduler);
}
/// <summary>
/// determines if the application is currently on the UI thread
/// </summary>
private static bool OnUIThread
{
get
{
if (FrameworkApplication.TestMode)
return QueuedTask.OnWorker;
else
return System.Windows.Application.Current.Dispatcher.CheckAccess();
}
}
#endregion
I will try drag and drop and some other test cases next, but in general I would recommend embedding all custom code in try {} catch {} to prevent crashes that are caused by uncaught exceptions with no error message.
