diff --git a/src/Avalonia.Base/Data/Converters/DefaultValueConverter.cs b/src/Avalonia.Base/Data/Converters/DefaultValueConverter.cs
index 990a4b04f2..0ffd6a9539 100644
--- a/src/Avalonia.Base/Data/Converters/DefaultValueConverter.cs
+++ b/src/Avalonia.Base/Data/Converters/DefaultValueConverter.cs
@@ -31,7 +31,7 @@ namespace Avalonia.Data.Converters
         {
             if (value == null)
             {
-                return AvaloniaProperty.UnsetValue;
+                return targetType.IsValueType ? AvaloniaProperty.UnsetValue : null;
             }
 
             if (typeof(ICommand).IsAssignableFrom(targetType) && value is Delegate d && d.Method.GetParameters().Length <= 1)
diff --git a/src/Avalonia.Controls/ListBox.cs b/src/Avalonia.Controls/ListBox.cs
index 3150b6be91..f26cd47bcb 100644
--- a/src/Avalonia.Controls/ListBox.cs
+++ b/src/Avalonia.Controls/ListBox.cs
@@ -68,7 +68,13 @@ namespace Avalonia.Controls
         /// <inheritdoc/>
         public new IList SelectedItems => base.SelectedItems;
 
-        /// <inheritdoc/>
+        /// <summary>
+        /// Gets or sets the selection mode.
+        /// </summary>
+        /// <remarks>
+        /// Note that the selection mode only applies to selections made via user interaction.
+        /// Multiple selections can be made programatically regardless of the value of this property.
+        /// </remarks>
         public new SelectionMode SelectionMode
         {
             get { return base.SelectionMode; }
diff --git a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
index 91a9fa7e40..4f01f5467b 100644
--- a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
@@ -222,6 +222,10 @@ namespace Avalonia.Controls.Primitives
         /// <summary>
         /// Gets or sets the selection mode.
         /// </summary>
+        /// <remarks>
+        /// Note that the selection mode only applies to selections made via user interaction.
+        /// Multiple selections can be made programatically regardless of the value of this property.
+        /// </remarks>
         protected SelectionMode SelectionMode
         {
             get { return GetValue(SelectionModeProperty); }
@@ -338,24 +342,36 @@ namespace Avalonia.Controls.Primitives
         {
             base.OnContainersMaterialized(e);
 
-            var selectedIndex = SelectedIndex;
-            var selectedContainer = e.Containers
-                .FirstOrDefault(x => (x.ContainerControl as ISelectable)?.IsSelected == true);
+            var resetSelectedItems = false;
 
-            if (selectedContainer != null)
+            foreach (var container in e.Containers)
             {
-                SelectedIndex = selectedContainer.Index;
-            }
-            else if (selectedIndex >= e.StartingIndex &&
-                     selectedIndex < e.StartingIndex + e.Containers.Count)
-            {
-                var container = e.Containers[selectedIndex - e.StartingIndex];
+                if ((container.ContainerControl as ISelectable)?.IsSelected == true)
+                {
+                    if (SelectedIndex == -1)
+                    {
+                        SelectedIndex = container.Index;
+                    }
+                    else
+                    {
+                        if (_selection.Add(container.Index))
+                        {
+                            resetSelectedItems = true;
+                        }
+                    }
 
-                if (container.ContainerControl != null)
+                    MarkContainerSelected(container.ContainerControl, true);
+                }
+                else if (_selection.Contains(container.Index))
                 {
                     MarkContainerSelected(container.ContainerControl, true);
                 }
             }
+
+            if (resetSelectedItems)
+            {
+                ResetSelectedItems();
+            }
         }
 
         /// <inheritdoc/>
diff --git a/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_DataValidation.cs b/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_DataValidation.cs
index b12b2e3c31..428f878945 100644
--- a/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_DataValidation.cs
+++ b/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_DataValidation.cs
@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Reactive.Subjects;
 using Avalonia.Data;
+using Avalonia.UnitTests;
 using Xunit;
 
 namespace Avalonia.Base.UnitTests
@@ -34,10 +35,10 @@ namespace Avalonia.Base.UnitTests
         {
             var target = new Class1();
 
-            target.SetValue(Class1.ValidatedDirectProperty, new BindingNotification(6));
-            target.SetValue(Class1.ValidatedDirectProperty, new BindingNotification(new Exception(), BindingErrorType.Error));
-            target.SetValue(Class1.ValidatedDirectProperty, new BindingNotification(new Exception(), BindingErrorType.DataValidationError));
-            target.SetValue(Class1.ValidatedDirectProperty, new BindingNotification(7));
+            target.SetValue(Class1.ValidatedDirectIntProperty, new BindingNotification(6));
+            target.SetValue(Class1.ValidatedDirectIntProperty, new BindingNotification(new Exception(), BindingErrorType.Error));
+            target.SetValue(Class1.ValidatedDirectIntProperty, new BindingNotification(new Exception(), BindingErrorType.DataValidationError));
+            target.SetValue(Class1.ValidatedDirectIntProperty, new BindingNotification(7));
 
             Assert.Equal(
                 new[]
@@ -73,7 +74,7 @@ namespace Avalonia.Base.UnitTests
             var source = new Subject<object>();
             var target = new Class1
             {
-                [!Class1.ValidatedDirectProperty] = source.ToBinding(),
+                [!Class1.ValidatedDirectIntProperty] = source.ToBinding(),
             };
 
             source.OnNext(new BindingNotification(6));
@@ -92,6 +93,30 @@ namespace Avalonia.Base.UnitTests
                 target.Notifications.AsEnumerable());
         }
 
+        [Fact]
+        public void Bound_Validated_Direct_String_Property_Can_Be_Set_To_Null()
+        {
+            var source = new ViewModel
+            {
+                StringValue = "foo",
+            };
+
+            var target = new Class1
+            {
+                [!Class1.ValidatedDirectStringProperty] = new Binding
+                {
+                    Path = nameof(ViewModel.StringValue),
+                    Source = source,
+                },
+            };
+
+            Assert.Equal("foo", target.ValidatedDirectString);
+
+            source.StringValue = null;
+
+            Assert.Null(target.ValidatedDirectString);
+        }
+
         private class Class1 : AvaloniaObject
         {
             public static readonly StyledProperty<int> NonValidatedProperty =
@@ -104,15 +129,23 @@ namespace Avalonia.Base.UnitTests
                     o => o.NonValidatedDirect,
                     (o, v) => o.NonValidatedDirect = v);
 
-            public static readonly DirectProperty<Class1, int> ValidatedDirectProperty =
+            public static readonly DirectProperty<Class1, int> ValidatedDirectIntProperty =
                 AvaloniaProperty.RegisterDirect<Class1, int>(
-                    nameof(ValidatedDirect),
-                    o => o.ValidatedDirect,
-                    (o, v) => o.ValidatedDirect = v,
+                    nameof(ValidatedDirectInt),
+                    o => o.ValidatedDirectInt,
+                    (o, v) => o.ValidatedDirectInt = v,
+                    enableDataValidation: true);
+
+            public static readonly DirectProperty<Class1, string> ValidatedDirectStringProperty =
+                AvaloniaProperty.RegisterDirect<Class1, string>(
+                    nameof(ValidatedDirectString),
+                    o => o.ValidatedDirectString,
+                    (o, v) => o.ValidatedDirectString = v,
                     enableDataValidation: true);
 
             private int _nonValidatedDirect;
-            private int _direct;
+            private int _directInt;
+            private string _directString;
 
             public int NonValidated
             {
@@ -122,14 +155,20 @@ namespace Avalonia.Base.UnitTests
 
             public int NonValidatedDirect
             {
-                get { return _direct; }
+                get { return _directInt; }
                 set { SetAndRaise(NonValidatedDirectProperty, ref _nonValidatedDirect, value); }
             }
 
-            public int ValidatedDirect
+            public int ValidatedDirectInt
+            {
+                get { return _directInt; }
+                set { SetAndRaise(ValidatedDirectIntProperty, ref _directInt, value); }
+            }
+
+            public string ValidatedDirectString
             {
-                get { return _direct; }
-                set { SetAndRaise(ValidatedDirectProperty, ref _direct, value); }
+                get { return _directString; }
+                set { SetAndRaise(ValidatedDirectStringProperty, ref _directString, value); }
             }
 
             public IList<BindingNotification> Notifications { get; } = new List<BindingNotification>();
@@ -139,5 +178,16 @@ namespace Avalonia.Base.UnitTests
                 Notifications.Add(notification);
             }
         }
+
+        public class ViewModel : NotifyingBase
+        {
+            private string _stringValue;
+
+            public string StringValue
+            {
+                get { return _stringValue; }
+                set { _stringValue = value; RaisePropertyChanged(); }
+            }
+        }
     }
 }
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs
index 9d0cc368e0..2115072e6e 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs
@@ -53,7 +53,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         }
 
         [Fact]
-        public void Assigning_SelectedItems_Should_Set_SelectedIndex()
+        public void Assigning_Single_SelectedItems_Should_Set_SelectedIndex()
         {
             var target = new TestSelector
             {
@@ -62,9 +62,51 @@ namespace Avalonia.Controls.UnitTests.Primitives
             };
 
             target.ApplyTemplate();
+            target.Presenter.ApplyTemplate();
             target.SelectedItems = new AvaloniaList<object>("bar");
 
             Assert.Equal(1, target.SelectedIndex);
+            Assert.Equal(new[] { "bar" }, target.SelectedItems);
+            Assert.Equal(new[] { 1 }, SelectedContainers(target));
+        }
+
+        [Fact]
+        public void Assigning_Multiple_SelectedItems_Should_Set_SelectedIndex()
+        {
+            // Note that we don't need SelectionMode = Multiple here. Multiple selections can always
+            // be made in code.
+            var target = new TestSelector
+            {
+                Items = new[] { "foo", "bar", "baz" },
+                Template = Template(),
+            };
+
+            target.ApplyTemplate();
+            target.Presenter.ApplyTemplate();
+            target.SelectedItems = new AvaloniaList<string>("foo", "bar", "baz");
+
+            Assert.Equal(0, target.SelectedIndex);
+            Assert.Equal(new[] { "foo", "bar", "baz" }, target.SelectedItems);
+            Assert.Equal(new[] { 0, 1, 2 }, SelectedContainers(target));
+        }
+
+        [Fact]
+        public void Selected_Items_Should_Be_Marked_When_Panel_Created_After_SelectedItems_Is_Set()
+        {
+            // Issue #2565.
+            var target = new TestSelector
+            {
+                Items = new[] { "foo", "bar", "baz" },
+                Template = Template(),
+            };
+
+            target.ApplyTemplate();
+            target.SelectedItems = new AvaloniaList<string>("foo", "bar", "baz");
+            target.Presenter.ApplyTemplate();
+
+            Assert.Equal(0, target.SelectedIndex);
+            Assert.Equal(new[] { "foo", "bar", "baz" }, target.SelectedItems);
+            Assert.Equal(new[] { 0, 1, 2 }, SelectedContainers(target));
         }
 
         [Fact]
@@ -1026,6 +1068,31 @@ namespace Avalonia.Controls.UnitTests.Primitives
             Assert.Equal(1, target.SelectedItems.Count);
         }
 
+        [Fact]
+        public void Adding_Selected_ItemContainers_Should_Update_Selection()
+        {
+            var items = new AvaloniaList<ItemContainer>(new[]
+            {
+                new ItemContainer(),
+                new ItemContainer(),
+            });
+
+            var target = new TestSelector
+            {
+                Items = items,
+                Template = Template(),
+            };
+
+            target.ApplyTemplate();
+            target.Presenter.ApplyTemplate();
+            items.Add(new ItemContainer { IsSelected = true });
+            items.Add(new ItemContainer { IsSelected = true });
+
+            Assert.Equal(2, target.SelectedIndex);
+            Assert.Equal(items[2], target.SelectedItem);
+            Assert.Equal(new[] { items[2], items[3] }, target.SelectedItems);
+        }
+
         private IEnumerable<int> SelectedContainers(SelectingItemsControl target)
         {
             return target.Presenter.Panel.Children
@@ -1078,5 +1145,11 @@ namespace Avalonia.Controls.UnitTests.Primitives
             public List<string> Items { get; } 
             public List<string> SelectedItems { get; }
         }
+
+        private class ItemContainer : Control, ISelectable
+        {
+            public string Value { get; set; }
+            public bool IsSelected { get; set; }
+        }
     }
 }
diff --git a/tests/Avalonia.Controls.UnitTests/TextBoxTests.cs b/tests/Avalonia.Controls.UnitTests/TextBoxTests.cs
index f40571bc39..35f0b39210 100644
--- a/tests/Avalonia.Controls.UnitTests/TextBoxTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/TextBoxTests.cs
@@ -444,6 +444,22 @@ namespace Avalonia.Controls.UnitTests
             }
         }
 
+        [Fact]
+        public void Setting_Bound_Text_To_Null_Works()
+        {
+            using (UnitTestApplication.Start(Services))
+            {
+                var source = new Class1 { Bar = "bar" };
+                var target = new TextBox { DataContext = source };
+
+                target.Bind(TextBox.TextProperty, new Binding("Bar"));
+
+                Assert.Equal("bar", target.Text);
+                source.Bar = null;
+                Assert.Null(target.Text);
+            }
+        }
+
         private static TestServices FocusServices => TestServices.MockThreadingInterface.With(
             focusManager: new FocusManager(),
             keyboardDevice: () => new KeyboardDevice(),
@@ -492,12 +508,19 @@ namespace Avalonia.Controls.UnitTests
         private class Class1 : NotifyingBase
         {
             private int _foo;
+            private string _bar;
 
             public int Foo
             {
                 get { return _foo; }
                 set { _foo = value; RaisePropertyChanged(); }
             }
+
+            public string Bar
+            {
+                get { return _bar; }
+                set { _bar = value; RaisePropertyChanged(); }
+            }
         }
     }
 }