From 9a6cda66bcaa38fe58500320b5e16e71fcca07a2 Mon Sep 17 00:00:00 2001
From: Benedikt Schroeder <benedikt.schroeder@outlook.de>
Date: Sun, 29 Sep 2019 18:54:08 +0200
Subject: [PATCH 1/3] Add failing test for #2987

---
 .../Primitives/SelectingItemsControlTests.cs  | 22 +++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
index 4e4d92afdc..8f27ebe853 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
@@ -109,6 +109,28 @@ namespace Avalonia.Controls.UnitTests.Primitives
             Assert.True(items[1].IsSelected);
         }
 
+        [Fact]
+        public void Setting_SelectedIndex_During_Initialize_Should_Select_Item_When_AlwaysSelected_Is_Used()
+        {
+            var listBox = new ListBox
+            {
+                SelectionMode = SelectionMode.Single | SelectionMode.AlwaysSelected
+            };
+
+            listBox.BeginInit();
+
+            listBox.SelectedIndex = 1;
+            var items = new AvaloniaList<string>();
+            listBox.Items = items;
+            items.Add("A");
+            items.Add("B");
+            items.Add("C");
+
+            listBox.EndInit();
+
+            Assert.Equal("B", listBox.SelectedItem);
+        }
+
         [Fact]
         public void Setting_SelectedIndex_Before_ApplyTemplate_Should_Set_Item_IsSelected_True()
         {

From bcbe9c3dbd6e2eb824b9947d667096d98edbaca5 Mon Sep 17 00:00:00 2001
From: Benedikt Schroeder <benedikt.schroeder@outlook.de>
Date: Wed, 18 Sep 2019 19:01:48 +0200
Subject: [PATCH 2/3] Fix setting SelectedIndex in XAML

---
 .../Primitives/SelectingItemsControl.cs          | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
index cc0c5f52be..761a3f3b3d 100644
--- a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
@@ -304,6 +304,11 @@ namespace Avalonia.Controls.Primitives
         {
             base.ItemsCollectionChanged(sender, e);
 
+            if (_updateCount > 0)
+            {
+                return;
+            }
+
             switch (e.Action)
             {
                 case NotifyCollectionChangedAction.Add:
@@ -1071,13 +1076,16 @@ namespace Avalonia.Controls.Primitives
 
         private void UpdateFinished()
         {
-            if (_updateSelectedIndex != int.MinValue)
+            if (_updateSelectedItem != null)
             {
-                SelectedIndex = _updateSelectedIndex;
+                SelectedItem = _updateSelectedItem;
             }
-            else if (_updateSelectedItem != null)
+            else
             {
-                SelectedItem = _updateSelectedItem;
+                if (ItemCount > 0)
+                {
+                    SelectedIndex = _updateSelectedIndex != int.MinValue ? _updateSelectedIndex : 0;
+                }
             }
         }
 

From b42126b9e35cc5ce404963584fee95bc7f1b77c3 Mon Sep 17 00:00:00 2001
From: Benedikt Schroeder <benedikt.schroeder@outlook.de>
Date: Wed, 18 Sep 2019 19:22:23 +0200
Subject: [PATCH 3/3] Properly reset SelectedIndex after the DataContext
 changed

---
 src/Avalonia.Controls/Primitives/SelectingItemsControl.cs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
index 761a3f3b3d..a50175bdee 100644
--- a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
@@ -1082,7 +1082,11 @@ namespace Avalonia.Controls.Primitives
             }
             else
             {
-                if (ItemCount > 0)
+                if (ItemCount == 0 && SelectedIndex != -1)
+                {
+                    SelectedIndex = -1;
+                }
+                else
                 {
                     SelectedIndex = _updateSelectedIndex != int.MinValue ? _updateSelectedIndex : 0;
                 }