From 1f9bb75ed3a8ec4064984254f43827a83c9ece33 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 11 Sep 2019 13:34:02 +0200
Subject: [PATCH 1/3] Add setter for ListBox.SelectedItems.

It had been erroneously omitted.
---
 src/Avalonia.Controls/ListBox.cs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/ListBox.cs b/src/Avalonia.Controls/ListBox.cs
index f26cd47bcb..449ca18465 100644
--- a/src/Avalonia.Controls/ListBox.cs
+++ b/src/Avalonia.Controls/ListBox.cs
@@ -66,7 +66,11 @@ namespace Avalonia.Controls
         }
 
         /// <inheritdoc/>
-        public new IList SelectedItems => base.SelectedItems;
+        public new IList SelectedItems
+        {
+            get => base.SelectedItems;
+            set => base.SelectedItems = value;
+        }
 
         /// <summary>
         /// Gets or sets the selection mode.

From 33cf4187791f840644d9867a427919298b05ca32 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 11 Sep 2019 13:34:33 +0200
Subject: [PATCH 2/3] Added failing test for #2969.

---
 .../Primitives/SelectingItemsControlTests.cs  | 20 +++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
index f4f500b802..4e4d92afdc 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
@@ -921,6 +921,26 @@ namespace Avalonia.Controls.UnitTests.Primitives
             Assert.True(raised);
         }
 
+        [Fact]
+        public void Can_Set_Both_SelectedItem_And_SelectedItems_During_Initialization()
+        {
+            // Issue #2969.
+            var target = new ListBox();
+            var selectedItems = new List<object>();
+
+            target.BeginInit();
+            target.Template = Template();
+            target.Items = new[] { "Foo", "Bar", "Baz" };
+            target.SelectedItems = selectedItems;
+            target.SelectedItem = "Bar";
+            target.EndInit();
+
+            Assert.Equal("Bar", target.SelectedItem);
+            Assert.Equal(1, target.SelectedIndex);
+            Assert.Same(selectedItems, target.SelectedItems);
+            Assert.Equal(new[] { "Bar" }, selectedItems);
+        }
+
         private FuncControlTemplate Template()
         {
             return new FuncControlTemplate<SelectingItemsControl>((control, scope) =>

From 25ebbd63be20ade9dd90a0864046b0dbcb9a7667 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 11 Sep 2019 13:35:00 +0200
Subject: [PATCH 3/3] Allow both SelectedItem and SelectedItems to be bound.

Fixes #2969.
---
 .../Primitives/SelectingItemsControl.cs                | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
index 340947d2e1..2eedd29258 100644
--- a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
@@ -112,7 +112,7 @@ namespace Avalonia.Controls.Primitives
         private bool _syncingSelectedItems;
         private int _updateCount;
         private int _updateSelectedIndex;
-        private IList _updateSelectedItems;
+        private object _updateSelectedItem;
 
         /// <summary>
         /// Initializes static members of the <see cref="SelectingItemsControl"/> class.
@@ -160,7 +160,7 @@ namespace Avalonia.Controls.Primitives
                 else
                 {
                     _updateSelectedIndex = value;
-                    _updateSelectedItems = null;
+                    _updateSelectedItem = null;
                 }
             }
         }
@@ -183,7 +183,7 @@ namespace Avalonia.Controls.Primitives
                 }
                 else
                 {
-                    _updateSelectedItems = new AvaloniaList<object>(value);
+                    _updateSelectedItem = value;
                     _updateSelectedIndex = int.MinValue;
                 }
             }
@@ -1075,9 +1075,9 @@ namespace Avalonia.Controls.Primitives
             {
                 SelectedIndex = _updateSelectedIndex;
             }
-            else if (_updateSelectedItems != null)
+            else if (_updateSelectedItem != null)
             {
-                SelectedItems = _updateSelectedItems;
+                SelectedItem = _updateSelectedItem;
             }
         }