Skip rendering unknown feature form element types

Author: dotMorten

src/Toolkit/Toolkit/UI/Controls/FeatureForm/FeatureFormElementTemplateSelector.cs

@@ -27,6 +27,7 @@ internal class FeatureFormElementTemplateSelector : DataTemplateSelector
         private static DataTemplate DefaultFieldFormElementTemplate;
         private static DataTemplate DefaultGroupElementTemplate;
         private static DataTemplate DefaultTextFormElementTemplate;
+        private static DataTemplate UnsupportedFormElementTemplate;
 
         [DynamicDependency(nameof(Esri.ArcGISRuntime.Mapping.FeatureForms.FormElement.IsVisible), "Esri.ArcGISRuntime.Mapping.FeatureForms.FormElement", "Esri.ArcGISRuntime")]
         [DynamicDependency(nameof(Esri.ArcGISRuntime.Mapping.FeatureForms.FormElement.Label), "Esri.ArcGISRuntime.Mapping.FeatureForms.FormElement", "Esri.ArcGISRuntime")]
@@ -53,6 +54,10 @@ static FeatureFormElementTemplateSelector()
                 view.SetBinding(TextFormElementView.ElementProperty, Binding.SelfPath);
                 return view;
             });
+            UnsupportedFormElementTemplate = new DataTemplate(() =>
+            {
+                return new Grid() { IsVisible = false };
+            });
         }
 
         public FeatureFormElementTemplateSelector()
@@ -70,7 +75,7 @@ public FeatureFormElementTemplateSelector()
 
         protected override DataTemplate OnSelectTemplate(object item, BindableObject container)
         {
-            if(item is FieldFormElement)
+            if (item is FieldFormElement)
             {
                 return FieldFormElementTemplate;
             }
@@ -82,7 +87,7 @@ protected override DataTemplate OnSelectTemplate(object item, BindableObject con
             {
                 return TextFormElementTemplate;
             }
-            return null!;
+            return UnsupportedFormElementTemplate; // Renders empty / skips
         }
     }
 }

src/Toolkit/Toolkit/UI/Controls/FeatureForm/FormElementItemsControl.Windows.cs

@@ -26,6 +26,8 @@ namespace Esri.ArcGISRuntime.Toolkit.Primitives
     /// </summary>
     public partial class FormElementItemsControl : ItemsControl
     {
+        private static DataTemplate UnsupportedFormElementTemplate = new DataTemplate();
+
         /// <inheritdoc />
         protected override void PrepareContainerForItemOverride(DependencyObject element, object item)
         {
@@ -36,14 +38,18 @@ protected override void PrepareContainerForItemOverride(DependencyObject element
                 {
                     presenter.ContentTemplate = FieldFormElementTemplate;
                 }
-                if (item is TextFormElement)
+                else if (item is TextFormElement)
                 {
                     presenter.ContentTemplate = TextFormElementTemplate;
                 }
                 else if (item is GroupFormElement)
                 {
                     presenter.ContentTemplate = GroupFormElementTemplate;
                 }
+                else
+                {
+                    presenter.ContentTemplate = UnsupportedFormElementTemplate; // Renders empty / skips
+                }
             }
         }