Implement test to delete child element and make it pass.

Tests/ViewModels/SettingsViewModelTest.cs

@@ -127,6 +127,32 @@ namespace Tests.ViewModels
                 "Settings' Element collection still contains the element model.");
         }
 
+        [Test]
+        public void DeleteChildElement()
+        {
+            Settings settings = new Settings();
+            settings.AddElement(new SelectFirstDay(new Items()));
+            settings.AddElement(new SelectEachDay());
+            settings.AddElement(new SelectLastDay());
+            SettingsViewModel settingsVM = new SettingsViewModel(settings);
+            ControlElementViewModel parent = ((ControlElementViewModel)settingsVM.Elements.First());
+            int oldCount = parent.Elements.Count;
+            ElementViewModel elementVM = ((ControlElementViewModel)settingsVM.Elements.First())
+                .Elements.First();
+            ElementBase element = elementVM.RevealModelObject() as ElementBase;
+            Assert.IsTrue(((ControlElementBase)settings.Elements[0]).FormatElements.Contains(element),
+                "Settings object does not contain the model that the VM revealed?!");
+            elementVM.IsSelected = true;
+            Assert.IsTrue(settingsVM.DeleteElementCommand.CanExecute(null),
+                "DeleteElementCommand should be enabled.");
+            settingsVM.DeleteElementCommand.Execute(null);
+            Assert.AreEqual(oldCount - 1, parent.Elements.Count);
+            Assert.IsFalse(parent.Elements.Contains(elementVM),
+                "Elements collection still contains the deleted element view model.");
+            Assert.IsFalse(((ControlElementBase)settings.Elements[0]).FormatElements.Contains(element),
+                "Settings' collection of FormatElement children still contains the element model.");
+        }
+
         [Test]
         public void CopyElement()
         {

zaaReloaded2/ViewModels/SettingsViewModel.cs

@@ -135,6 +135,7 @@ namespace zaaReloaded2.ViewModels
                     vm = new ControlElementViewModel(element as ControlElementBase);
                     foreach (FormatElementViewModel childVM in ((ControlElementViewModel)vm).Elements)
                     {
+                        childVM.Parent = vm as ControlElementViewModel;
                         childVM.PropertyChanged += ElementViewModel_PropertyChanged;
                     }
                 }