NavigationView: Fix app crash in Top mode when clearing the item coll…

…ection while a selected item exists (microsoft/microsoft-ui-xaml#3202)
l5624 · Sep 6, 2020 · c5e16e1 · c5e16e1
1 parent 625ac5c
commit c5e16e1
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Showing 2 changed files with 45 additions and 2 deletions.
diff --git a/ModernWpf.Controls/NavigationView/NavigationView.cs b/ModernWpf.Controls/NavigationView/NavigationView.cs
@@ -286,9 +286,10 @@ void OnSelectionModelSelectionChanged(SelectionModel selectionModel, SelectionMo
 
             if (IsTopNavigationView())
             {
-                var inMainMenu = selectedIndex.GetAt(0) == c_mainMenuBlockIndex;
                 // If selectedIndex does not exist, means item is being deselected through API
-                var isInOverflow = (selectedIndex != null && selectedIndex.GetSize() > 0) ? inMainMenu && !m_topDataProvider.IsItemInPrimaryList(selectedIndex.GetAt(1)) : false;
+                var isInOverflow = (selectedIndex != null && selectedIndex.GetSize() > 1)
+                    ? selectedIndex.GetAt(0) == c_mainMenuBlockIndex && !m_topDataProvider.IsItemInPrimaryList(selectedIndex.GetAt(1))
+                    : false;
                 if (isInOverflow)
                 {
                     // We only want to close the overflow flyout and move the item on selection if it is a leaf node

diff --git a/test/ModernWpfTestApp/ApiTests/NavigationViewTests.cs b/test/ModernWpfTestApp/ApiTests/NavigationViewTests.cs
@@ -879,5 +879,47 @@ public void VerifyOverflowButtonToolTip()
                 Verify.IsTrue(testCondition, "ToolTip text should have been \"More\".");
             });
         }
+
+        [TestMethod]
+        public void VerifyClearingItemsCollectionDoesNotCrashWhenItemSelectedOnTopNav()
+        {
+            RunOnUIThread.Execute(() =>
+            {
+                var navView = new NavigationView();
+                navView.PaneDisplayMode = NavigationViewPaneDisplayMode.Top;
+
+                var navViewItem1 = new NavigationViewItem() { Content = "MenuItem 1", };
+                var navViewItem2 = new NavigationViewItem() { Content = "MenuItem 2" };
+
+                Log.Comment("Set up the MenuItems collection");
+                navView.MenuItems.Add(navViewItem1);
+                navView.MenuItems.Add(navViewItem2);
+
+                Content = navView;
+                Content.UpdateLayout();
+
+                Log.Comment("Set MenuItem 1 as selected");
+                navView.SelectedItem = navViewItem1;
+                Verify.AreEqual(navViewItem1, navView.SelectedItem, "MenuItem 1 should have been selected");
+
+                // Clearing the MenuItems collection should not crash the app
+                Log.Comment("Clear the MenuItems collection");
+                navView.MenuItems.Clear();
+
+                Log.Comment("Set up the MenuItemsSource collection");
+                var itemsSource = new ObservableCollection<NavigationViewItem>() { navViewItem1, navViewItem2 };
+                navView.MenuItemsSource = itemsSource;
+
+                Content.UpdateLayout();
+
+                Log.Comment("Set MenuItem 1 as selected");
+                navView.SelectedItem = navViewItem1;
+                Verify.AreEqual(navViewItem1, navView.SelectedItem, "MenuItem 1 should have been selected");
+
+                // Clearing the MenuItemsSource collection should not crash the app
+                Log.Comment("Clear the MenuItemsSource collection");
+                itemsSource.Clear();
+            });
+        }
     }
 }