From 508883aa4c534f803215b396d621d52b37ca10a5 Mon Sep 17 00:00:00 2001
From: John Boyer <git@johntboyer.com>
Date: Sun, 9 Oct 2022 22:03:05 +1100
Subject: [PATCH 1/2] Addresses #8970, Fixes DataGrid not processing all new
 items when collection has changed.

---
 .../Collections/DataGridCollectionView.cs       | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/src/Avalonia.Controls.DataGrid/Collections/DataGridCollectionView.cs b/src/Avalonia.Controls.DataGrid/Collections/DataGridCollectionView.cs
index 906ec661ae..41d7883047 100644
--- a/src/Avalonia.Controls.DataGrid/Collections/DataGridCollectionView.cs
+++ b/src/Avalonia.Controls.DataGrid/Collections/DataGridCollectionView.cs
@@ -3412,8 +3412,7 @@ namespace Avalonia.Collections
                 RefreshOrDefer();
                 return;
             }
-
-            object addedItem = args.NewItems?[0];
+            
             object removedItem = args.OldItems?[0];
 
             // fire notifications for removes
@@ -3424,11 +3423,17 @@ namespace Avalonia.Collections
             }
 
             // fire notifications for adds
-            if ((args.Action == NotifyCollectionChangedAction.Add ||
-                args.Action == NotifyCollectionChangedAction.Replace) &&
-                (Filter == null || PassesFilter(addedItem)))
+            if (args.NewItems != null && 
+                (args.Action == NotifyCollectionChangedAction.Add ||
+                 args.Action == NotifyCollectionChangedAction.Replace))
             {
-                ProcessAddEvent(addedItem, args.NewStartingIndex);
+                for (var i = 0; i < args.NewItems.Count; i++)
+                {
+                    if (Filter == null || PassesFilter(args.NewItems[i]))
+                    {
+                        ProcessAddEvent(args.NewItems[i], args.NewStartingIndex + i);
+                    }
+                }
             }
             if (args.Action != NotifyCollectionChangedAction.Replace)
             {

From 1a9ed2052aaeea6386a12523239d7d22aeb6dae3 Mon Sep 17 00:00:00 2001
From: John Boyer <git@johntboyer.com>
Date: Mon, 10 Oct 2022 18:04:54 +1100
Subject: [PATCH 2/2] Fixed DataGrid not properly removing multiple items on
 collection changed.

---
 .../Collections/DataGridCollectionView.cs            | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/Avalonia.Controls.DataGrid/Collections/DataGridCollectionView.cs b/src/Avalonia.Controls.DataGrid/Collections/DataGridCollectionView.cs
index 41d7883047..30517f4b00 100644
--- a/src/Avalonia.Controls.DataGrid/Collections/DataGridCollectionView.cs
+++ b/src/Avalonia.Controls.DataGrid/Collections/DataGridCollectionView.cs
@@ -3413,13 +3413,15 @@ namespace Avalonia.Collections
                 return;
             }
             
-            object removedItem = args.OldItems?[0];
-
             // fire notifications for removes
-            if (args.Action == NotifyCollectionChangedAction.Remove ||
-                args.Action == NotifyCollectionChangedAction.Replace)
+            if (args.OldItems != null && 
+                (args.Action == NotifyCollectionChangedAction.Remove ||
+                args.Action == NotifyCollectionChangedAction.Replace))
             {
-                ProcessRemoveEvent(removedItem, args.Action == NotifyCollectionChangedAction.Replace);
+                foreach (var removedItem in args.OldItems)
+                {
+                    ProcessRemoveEvent(removedItem, args.Action == NotifyCollectionChangedAction.Replace);
+                }
             }
 
             // fire notifications for adds