From 5ac25a26f4ee09fd37fd2b3fc386134e884a30a7 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 11 Sep 2020 17:08:22 +0200
Subject: [PATCH] Tweak raising SelectedIndex/Item property changed.

---
 .../Primitives/SelectingItemsControl.cs       |  2 +-
 .../Selection/SelectionModel.cs               | 42 ++++++++++++-------
 2 files changed, 27 insertions(+), 17 deletions(-)

diff --git a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
index 5f8c5da2f8..fcef3b1d08 100644
--- a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
@@ -613,7 +613,7 @@ namespace Avalonia.Controls.Primitives
                 RaisePropertyChanged(SelectedIndexProperty, _oldSelectedIndex, SelectedIndex);
                 _oldSelectedIndex = SelectedIndex;
             }
-            else if (e.PropertyName == nameof(ISelectionModel.SelectedItem))
+            else if (e.PropertyName == nameof(ISelectionModel.SelectedItem) && _oldSelectedItem != SelectedItem)
             {
                 RaisePropertyChanged(SelectedItemProperty, _oldSelectedItem, SelectedItem);
                 _oldSelectedItem = SelectedItem;
diff --git a/src/Avalonia.Controls/Selection/SelectionModel.cs b/src/Avalonia.Controls/Selection/SelectionModel.cs
index 2556bd4c4c..2181b322b4 100644
--- a/src/Avalonia.Controls/Selection/SelectionModel.cs
+++ b/src/Avalonia.Controls/Selection/SelectionModel.cs
@@ -345,7 +345,9 @@ namespace Avalonia.Controls.Selection
                 LostSelection(this, EventArgs.Empty);
             }
 
-            CommitOperation(update.Operation);
+            // Don't raise PropertyChanged events here as the OnSourceCollectionChanged event that
+            // let to this method being called will raise them if necessary.
+            CommitOperation(update.Operation, raisePropertyChanged: false);
         }
 
         private protected override CollectionChangeState OnItemsAdded(int index, IList items)
@@ -430,6 +432,11 @@ namespace Avalonia.Controls.Selection
                 RaisePropertyChanged(nameof(SelectedIndex));
             }
 
+            if (e.Action == NotifyCollectionChangedAction.Remove && e.OldStartingIndex <= oldSelectedIndex)
+            {
+                RaisePropertyChanged(nameof(SelectedItem));
+            }
+
             if (oldAnchorIndex != _anchorIndex)
             {
                 RaisePropertyChanged(nameof(AnchorIndex));
@@ -611,7 +618,7 @@ namespace Avalonia.Controls.Selection
             }
         }
 
-        private void CommitOperation(Operation operation)
+        private void CommitOperation(Operation operation, bool raisePropertyChanged = true)
         {
             try
             {
@@ -679,23 +686,26 @@ namespace Avalonia.Controls.Selection
                     }
                 }
 
-                if (oldSelectedIndex != _selectedIndex)
+                if (raisePropertyChanged)
                 {
-                    indexesChanged = true;
-                    RaisePropertyChanged(nameof(SelectedIndex));
-                    RaisePropertyChanged(nameof(SelectedItem));
-                }
+                    if (oldSelectedIndex != _selectedIndex)
+                    {
+                        indexesChanged = true;
+                        RaisePropertyChanged(nameof(SelectedIndex));
+                        RaisePropertyChanged(nameof(SelectedItem));
+                    }
 
-                if (oldAnchorIndex != _anchorIndex)
-                {
-                    indexesChanged = true;
-                    RaisePropertyChanged(nameof(AnchorIndex));
-                }
+                    if (oldAnchorIndex != _anchorIndex)
+                    {
+                        indexesChanged = true;
+                        RaisePropertyChanged(nameof(AnchorIndex));
+                    }
 
-                if (indexesChanged)
-                {
-                    RaisePropertyChanged(nameof(SelectedIndexes));
-                    RaisePropertyChanged(nameof(SelectedItems));
+                    if (indexesChanged)
+                    {
+                        RaisePropertyChanged(nameof(SelectedIndexes));
+                        RaisePropertyChanged(nameof(SelectedItems));
+                    }
                 }
             }
             finally