MUX NavigationView should throw if WUXC NavViewItems are added to it (#…

…69) MUX NavigationView should throw if WUXC NavViewItems are added to it Use IsItemItsOwnContainerOverride as a hook to approximate list contents change events and deny any WUX items in the MUX list. [Internal Issue](https://microsoft.visualstudio.com/OS/ft_xamlcon/_workitems/edit/19017881)
microsoft · Jan 19, 2019 · 0e052f1 · 0e052f1
1 parent 8e7f7d6
commit 0e052f1
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Showing 2 changed files with 44 additions and 1 deletion.
diff --git a/dev/NavigationView/NavigationViewList.cpp b/dev/NavigationView/NavigationViewList.cpp
@@ -26,6 +26,15 @@ bool NavigationViewList::IsItemItsOwnContainerOverride(winrt::IInspectable const
     bool isItemItsOwnContainerOverride = false;
     if (args)
     {
+        // This validation is only relevant outside of the Windows build where WUXC and MUXC have distinct types.
+#if !BUILD_WINDOWS
+        // Certain items are disallowed in a NavigationView's items list. Check for them.
+        if (args.try_as<winrt::Windows::UI::Xaml::Controls::NavigationViewItemBase>())
+        {
+            throw winrt::hresult_invalid_argument(L"MenuItems contains a Windows.UI.Xaml.Controls.NavigationViewItem. This control requires that the NavigationViewItems be of type Microsoft.UI.Xaml.Controls.NavigationViewItem.");
+        }
+#endif
+
         auto nvib = args.try_as<winrt::NavigationViewItemBase>();
         if (nvib && nvib != m_lastItemCalledInIsItemItsOwnContainerOverride.get())
         {
@@ -56,6 +65,7 @@ void NavigationViewList::PrepareContainerForItemOverride(winrt::DependencyObject
         itemContainer.UseSystemFocusVisuals(m_showFocusVisual);
         winrt::get_self<NavigationViewItem>(itemContainer)->ClearIsContentChangeHandlingDelayedForTopNavFlag();
     }
+
     __super::PrepareContainerForItemOverride(element, item);
 }
 
@@ -133,4 +143,4 @@ void NavigationViewList::PropagateChangeToAllContainers(std::function<void(typen
             }
         }
     }
-}
+}
diff --git a/dev/NavigationView/NavigationView_ApiTests/NavigationViewTests.cs b/dev/NavigationView/NavigationView_ApiTests/NavigationViewTests.cs
@@ -3,6 +3,9 @@
 
 using MUXControlsTestApp.Utilities;
 
+using System;
+using System.Collections.Generic;
+using Windows.Foundation.Metadata;
 using Windows.UI.Xaml;
 using Windows.UI.Xaml.Controls;
 using Windows.UI.Xaml.Markup;
@@ -362,5 +365,35 @@ public void CanLoadSimpleNavigationView()
         }
 #endif
 
+#if !BUILD_WINDOWS
+        [TestMethod]
+        public void VerifyCanNotAddWUXItems()
+        {
+            if (!ApiInformation.IsTypePresent("Windows.UI.Xaml.Controls.NavigationViewItem"))
+            {
+                Log.Warning("WUX version of NavigationViewItem only available starting in RS3.");
+                return;
+            }
+
+            RunOnUIThread.Execute(() =>
+            {
+                var navView = new NavigationView();
+
+                var muxItem = new Microsoft.UI.Xaml.Controls.NavigationViewItem { Content = "MUX Item" };
+                navView.MenuItems.Add(muxItem);
+
+                navView.MenuItems.Add(new Microsoft.UI.Xaml.Controls.NavigationViewItemSeparator());
+
+                // No errors should occur here when we only use MUX items
+                navView.UpdateLayout();
+
+                var wuxItem = new Windows.UI.Xaml.Controls.NavigationViewItem { Content = "WUX Item" };
+                navView.MenuItems.Add(wuxItem);
+
+                // But adding a WUX item should generate an exception (as soon as the new item gets processed)
+                Verify.Throws<Exception>(() => { navView.UpdateLayout(); });
+            });
+        }
+#endif
     }
 }