topic Re: Error populating the fields for the selected layer in a dockpane in ArcGIS Pro SDK Questions

Error populating the fields for the selected layer in a dockpane

tzz_12 — Fri, 17 Mar 2023 19:19:01 GMT

Hi Everyone,

I am not sure why I am unable to populate the selected layer's fields. I have two combo boxes in my dockpane, layers in the map and selected layer fields. It's weird that when I comment out the GetFieldAsync() method, I am able to populate the feature layers on the active map, but when I don't comment the method out, then both the layer combo box and the selected layer's fields combo box does not show. If you can help me troubleshoot this problem, I would appreciate the help. Here is codes below:

private FeatureLayer _selectedLayer; // Selected feature layer public FeatureLayer SelectedLayer { get { return _selectedLayer; } set { SetProperty(ref _selectedLayer, value, () => SelectedLayer); _ = GetFieldsAsync(); } } private async Task GetFieldsAsync() { LayerFields.Clear(); SelectedField.Clear(); if (SelectedLayer == null) return; await QueuedTask.Run((Action)(() => { ObservableCollection<string> fields = new ObservableCollection<string>(); foreach (FieldDescription fd in SelectedLayer?.GetFieldDescriptions()) { string shapeField = SelectedLayer.GetFeatureClass().GetDefinition().GetShapeField(); if (fd.Name == shapeField) continue; fields.Add(fd.Name); } })); }

Re: Error populating the fields for the selected layer in a dockpane

Wolf — Fri, 17 Mar 2023 21:11:44 GMT

You are updating a list/combobox from a background thread, hence you have to take certain precautions. Like using:

System.Windows.Data.BindingOperations.EnableCollectionSynchronization(_layers, _lock);

This enables your observable collection for updates on non GUI threads. Also once you define and 'lock' an observable collection you can't assign a new collection (like you did with your field names). I attached a sample that shows FeatureLayers and field names on a Dockpane.

Re: Error populating the fields for the selected layer in a dockpane

tzz_12 — Mon, 20 Mar 2023 16:40:34 GMT

Hi Wolf,

Thanks for your help! After rereading your post, I understood what you meant. I am not able to open the example you attached. I recieved the following error message: "error : The project file cannot be opened. Unable to locate the .NET SDK. Check that it is installed and that the version specified in global.json (if any) matches the installed version." I have ArcGIS Pro SDK 2.8 installed. It looks like the SDK version does not match, most likely due to 3.x migration and SDK updates. Instead of creating a new collection, can you show me a short snippet of what I should be doing to see the layer's fields?

Thanks,

Thi

Re: Error populating the fields for the selected layer in a dockpane

Wolf — Mon, 20 Mar 2023 17:33:47 GMT

Hi Thi,

I attached a 2.9 sample that should build and run in 2.8. Remember that when you add data to the UI as a result of an Event (I.E. layer changed events) then very likely your code will run on a non-UI thread. Also anything within QueuedTask.Run is running on a non-UI thread.

Re: Error populating the fields for the selected layer in a dockpane

tzz_12 — Tue, 21 Mar 2023 00:39:30 GMT

For anyone having the same issue, I made a few changes to the DockpaneWithLayerFieldSelection, but both ways work:

internal class DockpaneWithLayerFieldSelectionViewModel : DockPane { private const string _dockPaneID = "DockpaneWithLayerFieldSelection_DockpaneWithLayerFieldSelection"; private ObservableCollection<FeatureLayer> _layers = new ObservableCollection<FeatureLayer>(); private ObservableCollection<string> _fieldNames = new ObservableCollection<string>(); private object _lock = new object(); protected DockpaneWithLayerFieldSelectionViewModel() { BindingOperations.EnableCollectionSynchronization(_layers, _lock); BindingOperations.EnableCollectionSynchronization(_fieldNames, _lock); LayersAddedEvent.Subscribe(OnLayersAdded); LayersRemovedEvent.Subscribe(OnLayersRemoved); ActiveMapViewChangedEvent.Subscribe(OnActiveMapViewChanged); // just in case the map is already up if (MapView.Active != null) { ActiveMapViewChangedEventArgs args = new ActiveMapViewChangedEventArgs(MapView.Active, null); OnActiveMapViewChanged(args); } } #region Bindings public ObservableCollection<FeatureLayer> Layers { get { return _layers; } } private FeatureLayer _selectedLayer; public FeatureLayer SelectedLayer { get { return _selectedLayer; } set { SetProperty(ref _selectedLayer, value, () => SelectedLayer); FieldNames.Clear(); if (SelectedLayer == null) return; QueuedTask.Run(() => { foreach (FieldDescription fd in SelectedLayer?.GetFieldDescriptions()) { string shapeField = SelectedLayer.GetFeatureClass().GetDefinition().GetShapeField(); if (fd.Name == shapeField) continue; FieldNames.Add(fd.Name); } }); } } public ObservableCollection<string> FieldNames { get { return _fieldNames; } } private string _selectedFieldName; public string SelectedFieldName { get { return _selectedFieldName; } set { SetProperty(ref _selectedFieldName, value, () => SelectedFieldName); Selection = string.Empty; if (SelectedFieldName == null) return; Selection = $@"{SelectedLayer.Name}.{SelectedFieldName}"; } } private string _Selection; public string Selection { get => _Selection; set => SetProperty(ref _Selection, value); } /// <summary> /// Text shown near the top of the DockPane. /// </summary> private string _heading = "Show Layer and Field Selection"; public string Heading { get => _heading; set => SetProperty(ref _heading, value); } #endregion #region Event Handlers /// <summary> /// The active map view changed, first clear layers and fields, then /// refresh with new layers if incomingView is not null /// </summary> /// <param name="args"></param> private void OnActiveMapViewChanged(ActiveMapViewChangedEventArgs args) { FieldNames.Clear(); Layers.Clear(); if (args.IncomingView != null) { var layers = args.IncomingView.Map.GetLayersAsFlattenedList().OfType<FeatureLayer>(); Layers.AddRange(layers); } } private void OnLayersRemoved(LayerEventsArgs args) { foreach (var layer in args.Layers.OfType<FeatureLayer>()) { if (Layers.Contains(layer)) Layers.Remove((FeatureLayer)layer); } } private void OnLayersAdded(LayerEventsArgs args) { foreach (var layer in args.Layers.OfType<FeatureLayer>()) { Layers.Add((FeatureLayer)layer); } } #endregion /// <summary> /// Show the DockPane. /// </summary> internal static void Show() { DockPane pane = FrameworkApplication.DockPaneManager.Find(_dockPaneID); if (pane == null) return; pane.Activate(); } } /// <summary> /// Button implementation to show the DockPane. /// </summary> internal class DockpaneWithLayerFieldSelection_ShowButton : Button { protected override void OnClick() { DockpaneWithLayerFieldSelectionViewModel.Show(); } } }