diff --git a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs index 5210362505..2fac60c8d8 100644 --- a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs +++ b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs @@ -7,6 +7,7 @@ using System.Linq; using System.Xml.Linq; using Avalonia.Controls.Generators; using Avalonia.Controls.Selection; +using Avalonia.Controls.Utils; using Avalonia.Data; using Avalonia.Input; using Avalonia.Input.Platform; @@ -66,6 +67,19 @@ namespace Avalonia.Controls.Primitives (o, v) => o.SelectedItem = v, defaultBindingMode: BindingMode.TwoWay, enableDataValidation: true); + /// + /// Defines the property + /// + public static readonly StyledProperty SelectedValueProperty = + AvaloniaProperty.Register(nameof(SelectedValue), + defaultBindingMode: BindingMode.TwoWay); + + /// + /// Defines the property + /// + public static readonly StyledProperty SelectedValueBindingProperty = + AvaloniaProperty.Register(nameof(SelectedValueBinding)); + /// /// Defines the property. /// @@ -129,6 +143,8 @@ namespace Avalonia.Controls.Primitives private bool _ignoreContainerSelectionChanged; private UpdateState? _updateState; private bool _hasScrolledToSelectedItem; + private BindingHelper? _bindingHelper; + private bool _isSelectionChangeActive; /// /// Initializes static members of the class. @@ -209,6 +225,19 @@ namespace Avalonia.Controls.Primitives } } + [AssignBinding] + public IBinding? SelectedValueBinding + { + get => GetValue(SelectedValueBindingProperty); + set => SetValue(SelectedValueBindingProperty, value); + } + + public object? SelectedValue + { + get => GetValue(SelectedValueProperty); + set => SetValue(SelectedValueProperty, value); + } + /// /// Gets or sets the selected items. /// @@ -609,6 +638,60 @@ namespace Avalonia.Controls.Primitives { WrapFocus = WrapSelection; } + else if (change.Property == SelectedValueProperty) + { + if (_isSelectionChangeActive) + return; + + if (_updateState is not null) + { + _updateState.SelectedValue = change.NewValue; + return; + } + + SelectItemWithValue(change.NewValue); + } + else if (change.Property == SelectedValueBindingProperty) + { + var idx = SelectedIndex; + + // If no selection is active, don't do anything as SelectedValue is already null + if (idx == -1) + { + return; + } + + var value = change.GetNewValue(); + if (value is null) + { + // Clearing SelectedValueBinding makes the SelectedValue the item itself + SelectedValue = SelectedItem; + return; + } + + var selectedItem = SelectedItem; + + try + { + _isSelectionChangeActive = true; + + if (_bindingHelper is null) + { + _bindingHelper = new BindingHelper(value); + } + else + { + _bindingHelper.UpdateBinding(value); + } + + // Re-evaluate SelectedValue with the new binding + SelectedValue = _bindingHelper.Evaluate(selectedItem); + } + finally + { + _isSelectionChangeActive = false; + } + } } /// @@ -815,6 +898,10 @@ namespace Avalonia.Controls.Primitives new BindingValue(SelectedItems)); _oldSelectedItems = SelectedItems; } + else if (e.PropertyName == nameof(ISelectionModel.Source)) + { + ClearValue(SelectedValueProperty); + } } /// @@ -845,6 +932,11 @@ namespace Avalonia.Controls.Primitives Mark(i, false); } + if (!_isSelectionChangeActive) + { + UpdateSelectedValueFromItem(); + } + var route = BuildEventRoute(SelectionChangedEvent); if (route.HasHandlers) @@ -871,6 +963,109 @@ namespace Avalonia.Controls.Primitives } } + private void SelectItemWithValue(object? value) + { + if (ItemCount == 0 || _isSelectionChangeActive) + return; + + try + { + _isSelectionChangeActive = true; + var si = FindItemWithValue(value); + if (si != AvaloniaProperty.UnsetValue) + { + SelectedItem = si; + } + else + { + SelectedItem = null; + } + } + finally + { + _isSelectionChangeActive = false; + } + } + + private object FindItemWithValue(object? value) + { + if (ItemCount == 0 || value is null) + { + return AvaloniaProperty.UnsetValue; + } + + var items = Items; + var binding = SelectedValueBinding; + + if (binding is null) + { + // No SelectedValueBinding set, SelectedValue is the item itself + // Still verify the value passed in is in the Items list + var index = items!.IndexOf(value); + + if (index >= 0) + { + return value; + } + else + { + return AvaloniaProperty.UnsetValue; + } + } + + _bindingHelper ??= new BindingHelper(binding); + + // Matching UWP behavior, if duplicates are present, return the first item matching + // the SelectedValue provided + foreach (var item in items!) + { + var itemValue = _bindingHelper.Evaluate(item); + + if (itemValue.Equals(value)) + { + return item; + } + } + + return AvaloniaProperty.UnsetValue; + } + + private void UpdateSelectedValueFromItem() + { + if (_isSelectionChangeActive) + return; + + var binding = SelectedValueBinding; + var item = SelectedItem; + + if (binding is null || item is null) + { + // No SelectedValueBinding, SelectedValue is Item itself + try + { + _isSelectionChangeActive = true; + SelectedValue = item; + } + finally + { + _isSelectionChangeActive = false; + } + return; + } + + _bindingHelper ??= new BindingHelper(binding); + + try + { + _isSelectionChangeActive = true; + SelectedValue = _bindingHelper.Evaluate(item); + } + finally + { + _isSelectionChangeActive = false; + } + } + private void AutoScrollToSelectedItemIfNecessary() { if (AutoScrollToSelectedItem && @@ -1037,6 +1232,13 @@ namespace Avalonia.Controls.Primitives Selection.Clear(); } + if (state.SelectedValue.HasValue) + { + var item = FindItemWithValue(state.SelectedValue.Value); + if (item != AvaloniaProperty.UnsetValue) + state.SelectedItem = item; + } + if (state.SelectedIndex.HasValue) { SelectedIndex = state.SelectedIndex.Value; @@ -1098,6 +1300,7 @@ namespace Avalonia.Controls.Primitives { private Optional _selectedIndex; private Optional _selectedItem; + private Optional _selectedValue; public int UpdateCount { get; set; } public Optional Selection { get; set; } @@ -1122,6 +1325,54 @@ namespace Avalonia.Controls.Primitives _selectedIndex = default; } } + + public Optional SelectedValue + { + get => _selectedValue; + set + { + _selectedValue = value; + } + } + } + + /// + /// Helper class for evaluating a binding from an Item and IBinding instance + /// + private class BindingHelper : StyledElement + { + public BindingHelper(IBinding binding) + { + UpdateBinding(binding); + } + + public static readonly StyledProperty ValueProperty = + AvaloniaProperty.Register("Value"); + + public object Evaluate(object? dataContext) + { + dataContext = dataContext ?? throw new ArgumentNullException(nameof(dataContext)); + + // Only update the DataContext if necessary + if (!dataContext.Equals(DataContext)) + DataContext = dataContext; + + return GetValue(ValueProperty); + } + + public void UpdateBinding(IBinding binding) + { + _lastBinding = binding; + var ib = binding.Initiate(this, ValueProperty); + if (ib is null) + { + throw new InvalidOperationException("Unable to create binding"); + } + + BindingOperations.Apply(this, ValueProperty, ib, null); + } + + private IBinding? _lastBinding; } } }