Refactor DataGridAssist.ApplyMaterialDesignColumnStyles to use AP

The assist class now uses the attached properties associated with the corresponding DataGrid. Introduced a ColumnUpdater type and a private DP in order to have a reference to the DataGrid in the Columns_CollectionChanged() callback and to do proper housekeeping/cleanup to avoid memory leaks.

Author: nicolaihenriksen

MaterialDesignThemes.Wpf/DataGridAssist.cs

@@ -1,3 +1,4 @@
+using System.Collections.Specialized;
 using System.Windows.Media;
 
 namespace MaterialDesignThemes.Wpf;
@@ -187,79 +188,103 @@ public static void SetApplyMaterialDesignColumnStyles(DataGrid element, bool val
     public static bool GetApplyMaterialDesignColumnStyles(DataGrid element)
         => (bool) element.GetValue(ApplyMaterialDesignColumnStylesProperty);
 
+
+    private static readonly DependencyProperty ColumnUpdaterProperty
+        = DependencyProperty.RegisterAttached("ColumnUpdater", typeof(ColumnUpdater), typeof(DataGridAssist),
+            new PropertyMetadata(default(ColumnUpdater)));
+    private static void SetColumnUpdater(DependencyObject element, ColumnUpdater? value) => element.SetValue(ColumnUpdaterProperty, value);
+    private static ColumnUpdater? GetColumnUpdater(DependencyObject element) => (ColumnUpdater?) element.GetValue(ColumnUpdaterProperty);
+
     private static void ApplyMaterialDesignColumnStylesPropertyChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
     {
         var dataGrid = (DataGrid)d;
-
-        dataGrid.Columns.CollectionChanged -= Columns_CollectionChanged;
+        ColumnUpdater? columnUpdater = GetColumnUpdater(dataGrid);
+        if (columnUpdater is not { })
+        {
+            columnUpdater = new ColumnUpdater(dataGrid);
+        }
+        dataGrid.Columns.CollectionChanged -= columnUpdater.Columns_CollectionChanged;
         if (Equals(true, e.NewValue))
         {
-            dataGrid.Columns.CollectionChanged += Columns_CollectionChanged;    // Auto-generated columns are added later in the chain, thus we subscribe to changes.
+            SetColumnUpdater(dataGrid, columnUpdater);
+            dataGrid.Columns.CollectionChanged += columnUpdater.Columns_CollectionChanged;    // Auto-generated columns are added later in the chain, thus we subscribe to changes.
             foreach (var column in dataGrid.Columns)
             {
-                ApplyMaterialDesignColumnStyleForColumn(column);
+                ColumnUpdater.ApplyMaterialDesignColumnStyleForColumn(dataGrid, column);
             }
         }
-    }
-
-    private static void Columns_CollectionChanged(object? sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
-    {
-        foreach (DataGridColumn column in e.NewItems?.OfType<DataGridColumn>() ?? Enumerable.Empty<DataGridColumn>())
+        else
         {
-            ApplyMaterialDesignColumnStyleForColumn(column);
+            dataGrid.ClearValue(ColumnUpdaterProperty);
         }
     }
 
-    private static void ApplyMaterialDesignColumnStyleForColumn(DataGridColumn column)
+    private class ColumnUpdater
     {
-        Style defaultElementStyle = (Style)DataGridBoundColumn.ElementStyleProperty.GetMetadata(column.GetType()).DefaultValue;
-        Style defaultEditingElementStyle = (Style)DataGridBoundColumn.EditingElementStyleProperty.GetMetadata(column.GetType()).DefaultValue;
+        private readonly DataGrid _dataGrid;
 
-        bool applyElementStyle;
-        bool applyEditingElementStyle;
-        switch (column)
+        public ColumnUpdater(DataGrid dataGrid) => _dataGrid = dataGrid;
+
+        public void Columns_CollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
+        {
+            foreach (DataGridColumn column in e.NewItems?.OfType<DataGridColumn>() ?? Enumerable.Empty<DataGridColumn>())
+            {
+                ApplyMaterialDesignColumnStyleForColumn(_dataGrid, column);
+            }
+        }
+
+        public static void ApplyMaterialDesignColumnStyleForColumn(DataGrid dataGrid, DataGridColumn column)
         {
-            case DataGridCheckBoxColumn checkBoxColumn:
-                applyElementStyle = Equals(checkBoxColumn.ElementStyle, defaultElementStyle);
-                applyEditingElementStyle = Equals(checkBoxColumn.EditingElementStyle, defaultEditingElementStyle);
-                if (applyElementStyle)
-                {
-                    checkBoxColumn.ElementStyle =  (Style)Application.Current.TryFindResource("MaterialDesignDataGridCheckBoxColumnStyle");
-                }
-
-                if (applyEditingElementStyle)
-                {
-                    checkBoxColumn.EditingElementStyle = (Style)Application.Current.TryFindResource("MaterialDesignDataGridCheckBoxColumnEditingStyle");
-                }
-                break;
-            case System.Windows.Controls.DataGridTextColumn textColumn:
-                applyElementStyle = Equals(textColumn.ElementStyle, defaultElementStyle);
-                applyEditingElementStyle = Equals(textColumn.EditingElementStyle, defaultEditingElementStyle);
-                if (applyElementStyle)
-                {
-                    textColumn.ElementStyle = (Style)Application.Current.TryFindResource("MaterialDesignDataGridTextColumnStyle");
-                }
-
-                if (applyEditingElementStyle)
-                {
-                    textColumn.EditingElementStyle = (Style)Application.Current.TryFindResource("MaterialDesignDataGridTextColumnEditingStyle");
-                }
-                break;
-            case System.Windows.Controls.DataGridComboBoxColumn comboBoxColumn:
-                applyElementStyle = Equals(comboBoxColumn.ElementStyle, defaultElementStyle);
-                applyEditingElementStyle = Equals(comboBoxColumn.EditingElementStyle, defaultEditingElementStyle);
-                if (applyElementStyle)
-                {
-                    comboBoxColumn.ElementStyle = (Style)Application.Current.TryFindResource(new ComponentResourceKey(typeof(ComboBox), "MaterialDataGridComboBoxColumnStyle"));
-                }
-
-                if (applyEditingElementStyle)
-                {
-                    comboBoxColumn.EditingElementStyle = (Style)Application.Current.TryFindResource(new ComponentResourceKey(typeof(ComboBox), "MaterialDataGridComboBoxColumnEditingStyle"));
-                }
-                break;
+            Style defaultElementStyle = (Style)DataGridBoundColumn.ElementStyleProperty.GetMetadata(column.GetType()).DefaultValue;
+            Style defaultEditingElementStyle = (Style)DataGridBoundColumn.EditingElementStyleProperty.GetMetadata(column.GetType()).DefaultValue;
+
+            bool applyElementStyle;
+            bool applyEditingElementStyle;
+            switch (column)
+            {
+                case DataGridCheckBoxColumn checkBoxColumn:
+                    applyElementStyle = Equals(checkBoxColumn.ElementStyle, defaultElementStyle);
+                    applyEditingElementStyle = Equals(checkBoxColumn.EditingElementStyle, defaultEditingElementStyle);
+                    if (applyElementStyle && GetAutoGeneratedCheckBoxStyle(dataGrid) is { } checkBoxElementStyle)
+                    {
+                        checkBoxColumn.ElementStyle = checkBoxElementStyle;
+                    }
+
+                    if (applyEditingElementStyle && GetAutoGeneratedEditingCheckBoxStyle(dataGrid) is { } checkBoxEditingElementStyle)
+                    {
+                        checkBoxColumn.EditingElementStyle = checkBoxEditingElementStyle;
+                    }
+                    break;
+                case System.Windows.Controls.DataGridTextColumn textColumn:
+                    applyElementStyle = Equals(textColumn.ElementStyle, defaultElementStyle);
+                    applyEditingElementStyle = Equals(textColumn.EditingElementStyle, defaultEditingElementStyle);
+                    if (applyElementStyle && GetAutoGeneratedTextStyle(dataGrid) is { } textElementStyle)
+                    {
+                        textColumn.ElementStyle = textElementStyle;
+                    }
+
+                    if (applyEditingElementStyle && GetAutoGeneratedEditingTextStyle(dataGrid) is { } textEditingElementStyle)
+                    {
+                        textColumn.EditingElementStyle = textEditingElementStyle;
+                    }
+                    break;
+                case System.Windows.Controls.DataGridComboBoxColumn comboBoxColumn:
+                    applyElementStyle = Equals(comboBoxColumn.ElementStyle, defaultElementStyle);
+                    applyEditingElementStyle = Equals(comboBoxColumn.EditingElementStyle, defaultEditingElementStyle);
+                    if (applyElementStyle && GetAutoGeneratedComboBoxStyle(dataGrid) is { } comboBoxElementStyle)
+                    {
+                        comboBoxColumn.ElementStyle = comboBoxElementStyle;
+                    }
+
+                    if (applyEditingElementStyle && GetAutoGeneratedEditingComboBoxStyle(dataGrid) is { } comboBoxEditingElementStyle)
+                    {
+                        comboBoxColumn.EditingElementStyle = comboBoxEditingElementStyle;
+                    }
+                    break;
+            }
         }
     }
+
     #endregion
 
     #region AttachedProperty : CellPaddingProperty

MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.DataGrid.xaml

@@ -549,6 +549,12 @@
       </Setter.Value>
     </Setter>
     <Setter Property="VerticalGridLinesBrush" Value="{Binding HorizontalGridLinesBrush, RelativeSource={RelativeSource Self}}" />
+    <Setter Property="wpf:DataGridAssist.AutoGeneratedCheckBoxStyle" Value="{StaticResource MaterialDesignDataGridCheckBoxColumnStyle}" />
+    <Setter Property="wpf:DataGridAssist.AutoGeneratedEditingCheckBoxStyle" Value="{StaticResource MaterialDesignDataGridCheckBoxColumnEditingStyle}" />
+    <Setter Property="wpf:DataGridAssist.AutoGeneratedEditingTextStyle" Value="{StaticResource MaterialDesignDataGridTextColumnEditingStyle}" />
+    <Setter Property="wpf:DataGridAssist.AutoGeneratedTextStyle" Value="{StaticResource MaterialDesignDataGridTextColumnStyle}" />
+    <Setter Property="wpf:DataGridAssist.AutoGeneratedEditingComboBoxStyle" Value="{x:Static wpf:DataGridComboBoxColumn.DefaultEditingElementStyle}" />
+    <Setter Property="wpf:DataGridAssist.AutoGeneratedComboBoxStyle" Value="{x:Static wpf:DataGridComboBoxColumn.DefaultElementStyle}" />
     <Setter Property="wpf:DataGridAssist.ApplyMaterialDesignColumnStyles" Value="true" />
     <Setter Property="wpf:DataGridAssist.EnableEditBoxAssist" Value="True" />
     <Setter Property="wpf:DataGridAssist.SelectedCellBorderBrush" Value="{DynamicResource MaterialDesignTextBoxBorder}" />