This example illustrates how to style the MasterDetailView expander cell and icon in WPF DataGrid (SfDataGrid).
WPF DataGrid (SfDataGrid) alloes you to change the style of expander cell and icon using DetailsViewDataGrid. You can change the expander cell border color by overriding the GridDetailsViewExpanderCell,GridDetailsViewIndentCell and GridHeaderIndentCell cells and change the BorderBrush property.
You can also change the DetailsViewDataGrid expander icon by change the Path property of GridDetailsViewExpanderCell.
<Window.Resources>
<Style TargetType="syncfusion:GridHeaderIndentCell">
<Setter Property="BorderBrush" Value="Red"/>
</Style>
<Style TargetType="syncfusion:GridDetailsViewIndentCell">
<Setter Property="BorderBrush" Value="Red"/>
</Style>
<Style TargetType="syncfusion:GridDetailsViewExpanderCell">
<Setter Property="Foreground" Value="#FF4D4D4D" />
<Setter Property="BorderBrush" Value="Red" />
<Setter Property="BorderThickness" Value="0,0,1,1" />
<Setter Property="FontSize" Value="12" />
<Setter Property="FocusVisualStyle" Value="{x:Null}" />
<Setter Property="IsTabStop" Value="False" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="syncfusion:GridDetailsViewExpanderCell">
<Border Background="Transparent"
BorderBrush="{TemplateBinding BorderBrush}"
BorderThickness="{TemplateBinding BorderThickness}"
Padding="{TemplateBinding Padding}">
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="ExpansionStates">
<VisualState x:Name="Expanded">
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="PART_CollapseCellPath" Storyboard.TargetProperty="(FrameworkElement.Visibility)">
<DiscreteObjectKeyFrame Value="{x:Static Visibility.Collapsed}" KeyTime="0:0:0"/>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="PART_ExpanderCellPath" Storyboard.TargetProperty="(FrameworkElement.Visibility)">
<DiscreteObjectKeyFrame Value="{x:Static Visibility.Visible}" KeyTime="0:0:0" />
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
<VisualState x:Name="Collapsed">
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="PART_CollapseCellPath" Storyboard.TargetProperty="(FrameworkElement.Visibility)">
<DiscreteObjectKeyFrame Value="{x:Static Visibility.Visible}" KeyTime="0:0:0"/>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetName="PART_ExpanderCellPath" Storyboard.TargetProperty="(FrameworkElement.Visibility)">
<DiscreteObjectKeyFrame Value="{x:Static Visibility.Collapsed}" KeyTime="0:0:0"/>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</VisualState>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Grid Background="{TemplateBinding Background}" Visibility="{TemplateBinding ExpanderIconVisibility}" Margin="{TemplateBinding Padding}">
<Path Margin="7" x:Name="PART_CollapseCellPath"
Width="{TemplateBinding Width}"
Height="{TemplateBinding Height}"
HorizontalAlignment="Center"
VerticalAlignment="Center"
Data="F1M1464.78,374.21C1466.31,374.21,1466.94,375.538,1466.17,376.861L1435.89,429.439C1435.12,430.759,1433.87,430.823,1433.11,429.5L1402.82,376.827C1402.06,375.507,1402.69,374.21,1404.21,374.21L1464.78,374.21"
Fill="{TemplateBinding Foreground}"
SnapsToDevicePixels="True"
Stretch="Fill"
Stroke="{TemplateBinding Foreground}"
UseLayoutRounding="False">
<Path.RenderTransform>
<TransformGroup>
<TransformGroup.Children>
<RotateTransform Angle="270" CenterX="4" CenterY="4" />
</TransformGroup.Children>
</TransformGroup>
</Path.RenderTransform>
</Path>
<Path x:Name="PART_ExpanderCellPath" Margin="7"
Width="{TemplateBinding Width}"
Height="{TemplateBinding Height}"
HorizontalAlignment="Center"
VerticalAlignment="Center"
Data="F1M1464.78,374.21C1466.31,374.21,1466.94,375.538,1466.17,376.861L1435.89,429.439C1435.12,430.759,1433.87,430.823,1433.11,429.5L1402.82,376.827C1402.06,375.507,1402.69,374.21,1404.21,374.21L1464.78,374.21"
Fill="{TemplateBinding Foreground}"
SnapsToDevicePixels="True"
Stretch="Fill"
Visibility="Collapsed"
Stroke="{TemplateBinding Foreground}"
UseLayoutRounding="False">
<Path.RenderTransform>
<TransformGroup>
<TransformGroup.Children>
<RotateTransform Angle="0" CenterX="4" CenterY="4" />
</TransformGroup.Children>
</TransformGroup>
</Path.RenderTransform>
</Path>
</Grid>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>```
KB article - [How to style the MasterDetailView expander cell and icon in WPF DataGrid (SfDataGrid)?](https://www.syncfusion.com/kb/11423/how-to-style-the-masterdetailview-expander-cell-and-icon-in-wpf-datagrid-sfdatagrid)
## Requirements to run the demo
Visual Studio 2015 and above versions