Related to this question: How to style the top-left corner of a DataGrid in XAML?
How to customize style for top-left corner of WPF-Toolkit's DataGrid
XAML:
<Window x:Class="Matrix_WPFToolkit_Test.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:toolkit="http://schemas.microsoft.com/wpf/2008/toolkit"
Title="MainWindow" Height="350" Width="525">
<Grid>
<toolkit:DataGrid x:Name="dataGrid" IsReadOnly="True" HeadersVisibility="All" GridLinesVisibility="All" CanUserAddRows="False" CanUserDeleteRows="False" CanUserReorderColumns="False" CanUserResizeColumns="False" CanUserResizeRows="False" CanUserSortColumns="False" SelectionMode="Single" SelectionUnit="Cell" RowDetailsVisibilityMode="Visible" SelectionChanged="dataGrid_SelectionChanged" Margin="-1,0,1.4,0.4" SelectedCellsChanged="dataGrid_SelectedCellsChanged">
<toolkit:DataGrid.RowHeaderTemplate>
<DataTemplate>
<TextBlock Text="1"/>
</DataTemplate>
</toolkit:DataGrid.RowHeaderTemplate>
<toolkit:DataGrid.ColumnHeaderStyle>
<Style TargetType="toolkit:DataGridColumnHeader">
<Setter Property="Background" Value="Gray"/>
<Setter Property="FontWeight" Value="Bold"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="BorderBrush" Value="Black"/>
</Style>
</toolkit:DataGrid.ColumnHeaderStyle>
<toolkit:DataGrid.RowHeaderStyle>
<Style TargetType="toolkit:DataGridRowHeader">
<Setter Property="Background" Value="Gray"/>
<Setter Property="FontWeight" Value="Bold"/>
</Style>
</toolkit:DataGrid.RowHeaderStyle>
<toolkit:DataGrid.CellStyle>
<Style TargetType="toolkit:DataGridCell">
<Setter Property="BorderThickness" Value="0"/>
<Setter Property="Background" Value="LightGray" />
<Setter Property="Foreground" Value="Black" />
<Style.Triggers>
<Trigger Property="IsSelected" Value="True">
<Setter Property="Background" Value="White"/>
</Trigger>
</Style.Triggers>
</Style>
</toolkit:DataGrid.CellStyle>
<toolkit:DataGrid.RowStyle>
<Style TargetType="toolkit:DataGridRow">
<Style.Triggers>
<Trigger Property="IsSelected" Value="True">
<Setter Property="BorderBrush" Value="Black" />
<Setter Property="BorderThickness" Value="0" />
</Trigger>
</Style.Triggers>
</Style>
</toolkit:DataGrid.RowStyle>
</toolkit:DataGrid>
</Grid>
Here I have customized the row header template, column heade style, cell selection style. How to style top-left corner cell in the data-grid (WPF Toolkit's)