Ensure selection is reported correctly during batch update.

src/Avalonia.Controls/SelectionModel.cs

@@ -629,6 +629,8 @@ namespace Avalonia.Controls
             {
                 AnchorIndex = default;
             }
+
+            OnSelectionChanged();
         }
 
         private void OnSelectionChanged(SelectionModelSelectionChangedEventArgs? e = null)
@@ -664,6 +666,8 @@ namespace Avalonia.Controls
             {
                 AnchorIndex = new IndexPath(index);
             }
+
+            OnSelectionChanged();
         }
 
         private void SelectWithGroupImpl(int groupIndex, int itemIndex, bool select)
@@ -680,6 +684,8 @@ namespace Avalonia.Controls
             {
                 AnchorIndex = new IndexPath(groupIndex, itemIndex);
             }
+
+            OnSelectionChanged();
         }
 
         private void SelectWithPathImpl(IndexPath index, bool select)
@@ -708,6 +714,8 @@ namespace Avalonia.Controls
             {
                 AnchorIndex = index;
             }
+
+            OnSelectionChanged();
         }
 
         private void SelectRangeFromAnchorImpl(int index, bool select)
@@ -721,6 +729,7 @@ namespace Avalonia.Controls
             }
 
             _rootNode.SelectRange(new IndexRange(anchorIndex, index), select);
+            OnSelectionChanged();
         }
 
         private void SelectRangeFromAnchorWithGroupImpl(int endGroupIndex, int endItemIndex, bool select)
@@ -754,6 +763,8 @@ namespace Avalonia.Controls
                 int endIndex = groupIdx == endGroupIndex ? endItemIndex : groupNode.DataCount - 1;
                 groupNode.SelectRange(new IndexRange(startIndex, endIndex), select);
             }
+
+            OnSelectionChanged();
         }
 
         private void SelectRangeImpl(IndexPath start, IndexPath end, bool select)
@@ -781,6 +792,8 @@ namespace Avalonia.Controls
                         info.ParentNode!.Select(info.Path.GetAt(info.Path.GetSize() - 1), select);
                     }
                 });
+
+            OnSelectionChanged();
         }
 
         private void BeginOperation()

tests/Avalonia.Controls.UnitTests/SelectionModelTests.cs

@@ -1512,6 +1512,47 @@ namespace Avalonia.Controls.UnitTests
             Assert.Equal(0, raised);
         }
 
+        [Fact]
+        public void Batch_Update_Selection_Is_Correct_Throughout()
+        {
+            var data = new[] { "foo", "bar", "baz", "qux" };
+            var target = new SelectionModel { Source = data };
+            var raised = 0;
+
+            using (target.Update())
+            {
+                target.Select(1);
+
+                Assert.Equal(new IndexPath(1), target.SelectedIndex);
+                Assert.Equal(new[] { new IndexPath(1) }, target.SelectedIndices);
+                Assert.Equal("bar", target.SelectedItem);
+                Assert.Equal(new[] { "bar" }, target.SelectedItems);
+
+                target.Deselect(1);
+
+                Assert.Equal(new IndexPath(), target.SelectedIndex);
+                Assert.Empty(target.SelectedIndices);
+                Assert.Null(target.SelectedItem);
+                Assert.Empty(target.SelectedItems);
+
+                target.SelectRange(new IndexPath(1), new IndexPath(1));
+
+                Assert.Equal(new IndexPath(1), target.SelectedIndex);
+                Assert.Equal(new[] { new IndexPath(1) }, target.SelectedIndices);
+                Assert.Equal("bar", target.SelectedItem);
+                Assert.Equal(new[] { "bar" }, target.SelectedItems);
+
+                target.ClearSelection();
+
+                Assert.Equal(new IndexPath(), target.SelectedIndex);
+                Assert.Empty(target.SelectedIndices);
+                Assert.Null(target.SelectedItem);
+                Assert.Empty(target.SelectedItems);
+            }
+
+            Assert.Equal(0, raised);
+        }
+
         [Fact]
         public void AutoSelect_Selects_When_Enabled()
         {