How to get an event for column resize invoked by user interaction (mouse left button + mouse move).
I tried SizeChanged event, but it is triggered also when new items are added to the DataGrid (with long text), but this case should not be handled.
<DataGrid.CellStyle>
<Style TargetType="DataGridCell">
<EventSetter Event="SizeChanged" Handler="DataGridCell_SizeChanged" />
</Style>
</DataGrid.CellStyle>
Thanks for any advice.
I used Blend to get the style for DataGrid all the way to DataGridColumnHeader and Thumb (DataGrid > DataGridColumnHeadersPresenter > DataGridColumnHeader > Thumb, ColumnHeaderGripperStyle). Then used Thumb x:Name="PART_RightHeaderGripper" and handled PreviewMouseLeftButtonDown and PreviewMouseMove events.
<Style x:Key="{ComponentResourceKey ResourceId=DataGridSelectAllButtonStyle, TypeInTargetAssembly={x:Type DataGrid}}" TargetType="{x:Type Button}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Button}">
<Grid>
<Rectangle x:Name="Border" Fill="{DynamicResource {x:Static SystemColors.ControlBrushKey}}" SnapsToDevicePixels="True"/>
<Polygon x:Name="Arrow" Fill="Black" HorizontalAlignment="Right" Margin="8,8,3,3" Opacity="0.15" Points="0,10 10,10 10,0" Stretch="Uniform" VerticalAlignment="Bottom"/>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Stroke" TargetName="Border" Value="{DynamicResource {x:Static SystemColors.ControlDarkBrushKey}}"/>
</Trigger>
<Trigger Property="IsPressed" Value="True">
<Setter Property="Fill" TargetName="Border" Value="{DynamicResource {x:Static SystemColors.ControlDarkBrushKey}}"/>
</Trigger>
<Trigger Property="IsEnabled" Value="False">
<Setter Property="Visibility" TargetName="Arrow" Value="Collapsed"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style x:Key="ColumnHeaderGripperStyle" TargetType="{x:Type Thumb}">
<Setter Property="Width" Value="8"/>
<Setter Property="Background" Value="Transparent"/>
<Setter Property="Cursor" Value="SizeWE"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Thumb}">
<Border Background="{TemplateBinding Background}" Padding="{TemplateBinding Padding}"/>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style x:Key="ThumbStyle1" TargetType="{x:Type Thumb}">
<Setter Property="Width" Value="8"/>
<Setter Property="Background" Value="Transparent"/>
<Setter Property="Cursor" Value="SizeWE"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Thumb}">
<Border Background="{TemplateBinding Background}" Padding="{TemplateBinding Padding}"/>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style x:Key="DataGridColumnHeaderStyle1" TargetType="{x:Type DataGridColumnHeader}">
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type DataGridColumnHeader}">
<Grid>
<theme:DataGridHeaderBorder Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" IsPressed="{TemplateBinding IsPressed}" IsHovered="{TemplateBinding IsMouseOver}" IsClickable="{TemplateBinding CanUserSort}" Padding="{TemplateBinding Padding}" SortDirection="{TemplateBinding SortDirection}" SeparatorVisibility="{TemplateBinding SeparatorVisibility}" SeparatorBrush="{TemplateBinding SeparatorBrush}">
<ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" RecognizesAccessKey="True" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
</theme:DataGridHeaderBorder>
<Thumb x:Name="PART_LeftHeaderGripper" HorizontalAlignment="Left" Style="{StaticResource ThumbStyle1}" />
<Thumb x:Name="PART_RightHeaderGripper" HorizontalAlignment="Right" Style="{StaticResource ColumnHeaderGripperStyle}"
PreviewMouseLeftButtonDown="PART_RightHeaderGripper_PreviewMouseLeftButtonDown"
PreviewMouseMove="PART_RightHeaderGripper_PreviewMouseMove"
/>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style x:Key="DataGridColumnHeadersPresenterStyle1" TargetType="{x:Type DataGridColumnHeadersPresenter}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type DataGridColumnHeadersPresenter}">
<Grid>
<DataGridColumnHeader Style="{DynamicResource DataGridColumnHeaderStyle1}" x:Name="PART_FillerColumnHeader" IsHitTestVisible="False"/>
<ItemsPresenter/>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style x:Key="DataGridStyle1" TargetType="{x:Type DataGrid}">
<Setter Property="Background" Value="{DynamicResource {x:Static SystemColors.ControlBrushKey}}"/>
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
<Setter Property="BorderBrush" Value="#FF688CAF"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="RowDetailsVisibilityMode" Value="VisibleWhenSelected"/>
<Setter Property="ScrollViewer.CanContentScroll" Value="true"/>
<Setter Property="ScrollViewer.PanningMode" Value="Both"/>
<Setter Property="Stylus.IsFlicksEnabled" Value="False"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type DataGrid}">
<Border Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Padding="{TemplateBinding Padding}" SnapsToDevicePixels="True">
<ScrollViewer x:Name="DG_ScrollViewer" Focusable="false">
<ScrollViewer.Template>
<ControlTemplate TargetType="{x:Type ScrollViewer}">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<Button Command="{x:Static DataGrid.SelectAllCommand}" Focusable="false" Style="{DynamicResource {ComponentResourceKey ResourceId=DataGridSelectAllButtonStyle, TypeInTargetAssembly={x:Type DataGrid}}}" Visibility="{Binding HeadersVisibility, ConverterParameter={x:Static DataGridHeadersVisibility.All}, Converter={x:Static DataGrid.HeadersVisibilityConverter}, RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}" Width="{Binding CellsPanelHorizontalOffset, RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}"/>
<DataGridColumnHeadersPresenter Style="{DynamicResource DataGridColumnHeadersPresenterStyle1}" x:Name="PART_ColumnHeadersPresenter" Grid.Column="1" Visibility="{Binding HeadersVisibility, ConverterParameter={x:Static DataGridHeadersVisibility.Column}, Converter={x:Static DataGrid.HeadersVisibilityConverter}, RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}"/>
<ScrollContentPresenter x:Name="PART_ScrollContentPresenter" CanContentScroll="{TemplateBinding CanContentScroll}" Grid.ColumnSpan="2" Grid.Row="1"/>
<ScrollBar x:Name="PART_VerticalScrollBar" Grid.Column="2" Maximum="{TemplateBinding ScrollableHeight}" Orientation="Vertical" Grid.Row="1" Value="{Binding VerticalOffset, Mode=OneWay, RelativeSource={RelativeSource Mode=TemplatedParent}}" ViewportSize="{TemplateBinding ViewportHeight}" Visibility="{TemplateBinding ComputedVerticalScrollBarVisibility}"/>
<Grid Grid.Column="1" Grid.Row="2">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="{Binding NonFrozenColumnsViewportHorizontalOffset, RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<ScrollBar x:Name="PART_HorizontalScrollBar" Grid.Column="1" Maximum="{TemplateBinding ScrollableWidth}" Orientation="Horizontal" Value="{Binding HorizontalOffset, Mode=OneWay, RelativeSource={RelativeSource Mode=TemplatedParent}}" ViewportSize="{TemplateBinding ViewportWidth}" Visibility="{TemplateBinding ComputedHorizontalScrollBarVisibility}"/>
</Grid>
</Grid>
</ControlTemplate>
</ScrollViewer.Template>
<ItemsPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
</ScrollViewer>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsGrouping" Value="true"/>
<Condition Property="VirtualizingPanel.IsVirtualizingWhenGrouping" Value="false"/>
</MultiTrigger.Conditions>
<Setter Property="ScrollViewer.CanContentScroll" Value="false"/>
</MultiTrigger>
</Style.Triggers>
</Style>