Fix AutoSuggestBox not setting SelectedItem

src/MaterialDesignThemes.Wpf/AutoSuggestBox.cs

@@ -96,7 +96,11 @@ public object SelectedItem
         set => SetValue(SelectedItemProperty, value);
     }
     public static readonly DependencyProperty SelectedItemProperty =
-        DependencyProperty.Register(nameof(SelectedItem), typeof(object), typeof(AutoSuggestBox), new PropertyMetadata(default(object)));
+        DependencyProperty.Register(
+            nameof(SelectedItem),
+            typeof(object),
+            typeof(AutoSuggestBox),
+            new FrameworkPropertyMetadata(default(object), FrameworkPropertyMetadataOptions.BindsTwoWayByDefault));
 
 
     public object SelectedValue
@@ -254,6 +258,7 @@ private bool CommitValueSelection(object? selectedValue)
         {
             CaretIndex = Text.Length;
         }
+        SetCurrentValue(SelectedItemProperty, selectedValue);
         CloseAutoSuggestionPopUp();
         var args = new RoutedPropertyChangedEventArgs<object?>(oldValue, Text)
         {

tests/MaterialDesignThemes.UITests/Samples/AutoSuggestBoxes/AutoSuggestTextBoxWithCollectionView.xaml

@@ -14,7 +14,9 @@
       materialDesign:HintAssist.HelperText="Name"
       materialDesign:TextFieldAssist.HasClearButton="True"
       Text="{Binding AutoSuggestText, UpdateSourceTrigger=PropertyChanged}"
-      Suggestions="{Binding Suggestions}">
+      Suggestions="{Binding Suggestions}"
+      SelectedItem="{Binding SelectedItem}"
+      >
     </materialDesign:AutoSuggestBox>
     <!--
     <ComboBox ItemsSource="{Binding Suggestions}"

tests/MaterialDesignThemes.UITests/Samples/AutoSuggestBoxes/AutoSuggestTextBoxWithCollectionView.xaml.cs

@@ -1,7 +1,7 @@
-using CommunityToolkit.Mvvm.ComponentModel;
-using System.Collections.ObjectModel;
+using System.Collections.ObjectModel;
 using System.ComponentModel;
 using System.Windows.Data;
+using CommunityToolkit.Mvvm.ComponentModel;
 
 namespace MaterialDesignThemes.UITests.Samples.AutoSuggestBoxes;
 
@@ -26,6 +26,9 @@ public partial class AutoSuggestTextBoxWithCollectionViewViewModel : ObservableO
     [ObservableProperty]
     private string? _autoSuggestText;
 
+    [ObservableProperty]
+    private string? _selectedItem;
+
     partial void OnAutoSuggestTextChanged(string? oldValue, string? newValue)
     {
         if (!string.IsNullOrWhiteSpace(newValue))
@@ -36,19 +39,19 @@ partial void OnAutoSuggestTextChanged(string? oldValue, string? newValue)
         {
             Suggestions.Filter = null;
         }
-        base.OnPropertyChanged(nameof(Suggestions));
+        OnPropertyChanged(nameof(Suggestions));
     }
 
     public AutoSuggestTextBoxWithCollectionViewViewModel()
     {
-        BaseSuggestions = new()
-        {
+        BaseSuggestions =
+        [
             "Apples",
             "Bananas",
             "Beans",
             "Mtn Dew",
             "Orange",
-        };
+        ];
         Suggestions = CollectionViewSource.GetDefaultView(BaseSuggestions);
     }
 

tests/MaterialDesignThemes.UITests/Samples/AutoSuggestBoxes/AutoSuggestTextBoxWithTemplate.xaml

@@ -8,7 +8,6 @@
              d:DataContext="{d:DesignInstance Type=local:AutoSuggestTextBoxWithTemplateViewModel}"
              mc:Ignorable="d" 
              d:DesignHeight="450" d:DesignWidth="800">
-  <!-- TODO SELECTED ITEM -->
   <materialDesign:AutoSuggestBox
       materialDesign:HintAssist.HelperText="Name"
       materialDesign:TextFieldAssist.HasClearButton="True"

tests/MaterialDesignThemes.UITests/Samples/AutoSuggestBoxes/AutoSuggestTextBoxWithTemplate.xaml.cs

@@ -21,7 +21,7 @@ public partial class AutoSuggestTextBoxWithTemplateViewModel : ObservableObject
     private List<SuggestionThing> BaseSuggestions { get; }
 
     [ObservableProperty]
-    private ObservableCollection<SuggestionThing> _suggestions = new();
+    private ObservableCollection<SuggestionThing> _suggestions = [];
 
     [ObservableProperty]
     private string? _autoSuggestText;
@@ -41,14 +41,14 @@ partial void OnAutoSuggestTextChanged(string? oldValue, string? newValue)
 
     public AutoSuggestTextBoxWithTemplateViewModel()
     {
-        BaseSuggestions = new()
-        {
+        BaseSuggestions =
+        [
             new("Apples"),
             new("Bananas"),
             new("Beans"),
             new("Mtn Dew"),
             new("Orange"),
-        };
+        ];
         Suggestions = new ObservableCollection<SuggestionThing>(BaseSuggestions);
     }
 
@@ -62,9 +62,7 @@ private static bool IsMatch(string item, string currentText)
     }
 }
 
-public class SuggestionThing
+public class SuggestionThing(string name)
 {
-    public string Name { get; }
-
-    public SuggestionThing(string name) => Name = name;
+    public string Name { get; } = name;
 }

tests/MaterialDesignThemes.UITests/WPF/AutoSuggestBoxes/AutoSuggestTextBoxTests.cs

@@ -1,4 +1,3 @@
-using System.Collections;
 using System.ComponentModel;
 using MaterialDesignThemes.UITests.Samples.AutoSuggestBoxes;
 using MaterialDesignThemes.UITests.Samples.AutoSuggestTextBoxes;
@@ -201,6 +200,38 @@ public async Task AutoSuggestBox_KeysUpAndDown_WrapAround()
         Assert.Equal(0, await suggestionListBox.GetSelectedIndex());
     }
 
+    [Fact]
+    [Description("Issue 3845")]
+    public async Task AutoSuggestBox_SelectingAnItem_SetsSelectedItem()
+    {
+        await using var recorder = new TestRecorder(App);
+
+        //Arrange
+        IVisualElement userControl = await LoadUserControl<AutoSuggestTextBoxWithCollectionView>();
+        IVisualElement<AutoSuggestBox> suggestBox = await userControl.GetElement<AutoSuggestBox>();
+        IVisualElement<Popup> popup = await suggestBox.GetElement<Popup>();
+        IVisualElement<ListBox> suggestionListBox = await popup.GetElement<ListBox>();
+
+        //Act
+        await suggestBox.MoveKeyboardFocus();
+        await Task.Delay(50);
+        await suggestBox.SendKeyboardInput($"B{Key.Down}{Key.Enter}");
+        await Task.Delay(50);
+
+        //Assert
+        string? selectedItem = (await suggestBox.GetSelectedItem()) as string;
+        Assert.Equal("Bananas", selectedItem);
+
+        static void AssertViewModelProperty(AutoSuggestBox autoSuggestBox)
+        {
+            var viewModel = (AutoSuggestTextBoxWithCollectionViewViewModel)autoSuggestBox.DataContext;
+            Assert.Equal("Bananas", viewModel.SelectedItem);
+        }
+        await suggestBox.RemoteExecute(AssertViewModelProperty);
+
+        recorder.Success();
+    }
+
     private static async Task AssertExists(IVisualElement<ListBox> suggestionListBox, string text, bool existsOrNotCheck = true)
     {
         try