Implement data grouping feature for WinUI TableView

src/TableView.Properties.cs

@@ -264,6 +264,26 @@
     /// </summary>
     public static readonly DependencyProperty ShowFilterItemsCountProperty =  DependencyProperty.Register(nameof(ShowFilterItemsCount), typeof(bool), typeof(TableView), new PropertyMetadata(false));
 
+    /// <summary>
+    /// Identifies the <see cref="GroupByPath"/> dependency property.
+    /// </summary>
+    public static readonly DependencyProperty GroupByPathProperty = DependencyProperty.Register(nameof(GroupByPath), typeof(string), typeof(TableView), new PropertyMetadata(null, OnGroupByPathChanged));
+
+    /// <summary>
+    /// Identifies the <see cref="ShowGroupHeaders"/> dependency property.
+    /// </summary>
+    public static readonly DependencyProperty ShowGroupHeadersProperty = DependencyProperty.Register(nameof(ShowGroupHeaders), typeof(bool), typeof(TableView), new PropertyMetadata(true, OnShowGroupHeadersChanged));
+
+    /// <summary>
+    /// Identifies the <see cref="GroupSortDirection"/> dependency property.
+    /// </summary>
+    public static readonly DependencyProperty GroupSortDirectionProperty = DependencyProperty.Register(nameof(GroupSortDirection), typeof(SortDirection), typeof(TableView), new PropertyMetadata(SortDirection.Ascending, OnGroupSortDirectionChanged));
+
+    /// <summary>
+    /// Identifies the <see cref="ShowGroupItemCount"/> dependency property.
+    /// </summary>
+    public static readonly DependencyProperty ShowGroupItemCountProperty = DependencyProperty.Register(nameof(ShowGroupItemCount), typeof(bool), typeof(TableView), new PropertyMetadata(true, OnShowGroupItemCountChanged));
+
     /// <summary>
     /// Gets or sets a value indicating whether opening the column filter over header right-click is enabled.
     /// </summary>
@@ -281,7 +301,43 @@
     /// <summary>
     /// Gets the collection of sort descriptions applied to the items.
     /// </summary>
+    /// <summary>
+    /// Gets or sets the property path used to group items in the TableView.
+    /// </summary>
+    public string? GroupByPath
+    {
+        get => (string?)GetValue(GroupByPathProperty);
+        set => SetValue(GroupByPathProperty, value);
+    }
+
+    /// <summary>
+    /// Gets or sets a value indicating whether group headers are shown.
+    /// </summary>
+    public bool ShowGroupHeaders
+    {
+        get => (bool)GetValue(ShowGroupHeadersProperty);
+        set => SetValue(ShowGroupHeadersProperty, value);
+    }
+
+    /// <summary>
+    /// Gets or sets the sorting direction used for grouping.
+    /// </summary>
+    public SortDirection GroupSortDirection
+    {
+        get => (SortDirection)GetValue(GroupSortDirectionProperty);
+        set => SetValue(GroupSortDirectionProperty, value);
+    }
+
+    /// <summary>
+    /// Gets or sets a value indicating whether group headers show item counts.
+    /// </summary>
+    public bool ShowGroupItemCount
+    {
+        get => (bool)GetValue(ShowGroupItemCountProperty);
+        set => SetValue(ShowGroupItemCountProperty, value);
+    }
+
     public IList<SortDescription> SortDescriptions => _collectionView.SortDescriptions;
 
     /// <summary>
     /// Gets the collection of filter descriptions applied to the items.
@@ -1097,12 +1153,65 @@
         }
     }
 
+    /// <summary>
+    /// Handles changes to the GroupByPath property.
+    /// </summary>
+    private static void OnGroupByPathChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+    {
+        if (d is TableView tableView)
+        {
+            tableView.EnsureGroupingSortDescription();
+            tableView.RebuildDisplayedItems();
+        }
+    }
+
+    /// <summary>
+    /// Handles changes to the ShowGroupHeaders property.
+    /// </summary>
+    private static void OnShowGroupHeadersChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+    {
+        if (d is TableView tableView)
+        {
+            tableView.RebuildDisplayedItems();
+        }
+    }
+
+    /// <summary>
+    /// Handles changes to the GroupSortDirection property.
+    /// </summary>
+    private static void OnGroupSortDirectionChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+    {
+        if (d is TableView tableView)
+        {
+            tableView.EnsureGroupingSortDescription();
+            tableView.RebuildDisplayedItems();
+        }
+    }
+
+    /// <summary>
+    /// Handles changes to the ShowGroupItemCount property.
+    /// </summary>
+    private static void OnShowGroupItemCountChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+    {
+        if (d is TableView tableView)
+        {
+            tableView.RebuildDisplayedItems();
+        }
+    }
+
     /// <summary>
     /// Throws an exception if the base ItemsSource property is set directly.
     /// </summary>
     private void OnBaseItemsSourceChanged(DependencyObject sender, DependencyProperty dp)
     {
-        throw new InvalidOperationException("Setting this property directly is not allowed. Use TableView.ItemsSource instead.");
+        if (_isUpdatingBaseItemsSource || ReferenceEquals(base.ItemsSource, _displayItems))
+        {
+            return;
+        }
+
+        _isUpdatingBaseItemsSource = true;
+        base.ItemsSource = _displayItems;
+        _isUpdatingBaseItemsSource = false;
     }
 
     /// <summary>