Merge pull request #1763 from AvaloniaUI/fixes/carousel-presenter-fix

Fix SelectingItemsControl

src/Avalonia.Controls/Primitives/SelectingItemsControl.cs

@@ -360,7 +360,7 @@ namespace Avalonia.Controls.Primitives
                     {
                         if (!AlwaysSelected)
                         {
-                            SelectedIndex = -1;
+                            selectedIndex = SelectedIndex = -1;
                         }
                         else
                         {
@@ -368,6 +368,11 @@ namespace Avalonia.Controls.Primitives
                         }
                     }
 
+                    var items = Items?.Cast<object>();
+                    if (selectedIndex >= items.Count())
+                    {
+                        selectedIndex = SelectedIndex = items.Count() - 1;
+                    }
                     break;
 
                 case NotifyCollectionChangedAction.Reset:

tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs

@@ -149,6 +149,34 @@ namespace Avalonia.Controls.UnitTests.Primitives
             Assert.Equal(1, target.SelectedIndex);
         }
 
+        [Fact]
+        public void SelectedIndex_Item_Is_Updated_As_Items_Removed_When_Last_Item_Is_Selected()
+        {
+            var items = new ObservableCollection<string>
+            {
+               "Foo",
+               "Bar",
+               "FooBar"
+            };
+
+            var target = new SelectingItemsControl
+            {
+                Items = items,
+                Template = Template(),
+            };
+
+            target.ApplyTemplate();
+            target.SelectedItem = items[2];
+
+            Assert.Equal(items[2], target.SelectedItem);
+            Assert.Equal(2, target.SelectedIndex);
+
+            items.RemoveAt(0);
+
+            Assert.Equal(items[1], target.SelectedItem);
+            Assert.Equal(1, target.SelectedIndex);
+        }
+
         [Fact]
         public void Setting_SelectedItem_To_Not_Present_Item_Should_Clear_Selection()
         {