Hello, do you mean you want to design a Grid or a DataGrid? Since you mentioned ShowGridLines, I assume it's a Grid. You can put a Rectangle with no Fill in each cell. Don't worry, you can still add other elements into the cell. Each cell can host arbitrary elements. Try something like this:
<Border Height="480" Width="640" CornerRadius="10,10,10,10" BorderBrush="#FFFF0000" BorderThickness="2,2,2,2">
<Grid x:Name="LayoutRoot" Height="480" Width="640" >
<Grid.ColumnDefinitions>
<ColumnDefinition Width="0.498*"/>
<ColumnDefinition Width="0.502*"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="0.498*"/>
<RowDefinition Height="0.502*"/>
</Grid.RowDefinitions>
<Rectangle HorizontalAlignment="Stretch" Margin="0,0,0,0" VerticalAlignment="Stretch" Stroke="#FF008BFF"/>
<Rectangle HorizontalAlignment="Stretch" Margin="0,0,0,0" VerticalAlignment="Stretch" Stroke="#FF008BFF" Grid.Column="1"/>
<Rectangle HorizontalAlignment="Stretch" Margin="0,0,0,0" VerticalAlignment="Stretch" Stroke="#FF008BFF" Grid.Row="1"/>
<Rectangle HorizontalAlignment="Stretch" Margin="0,0,0,0" VerticalAlignment="Stretch" Stroke="#FF008BFF" Grid.Row="1" Grid.Column="1"/>
<Button HorizontalAlignment="Stretch" Margin="38,70,65.7200012207031,88.0400009155273" VerticalAlignment="Stretch" Content="Other Contents for this cell"/>
<Button HorizontalAlignment="Stretch" Margin="38,70,65.7200012207031,88.0400009155273" VerticalAlignment="Stretch" Content="Other Contents for this cell" Grid.Row="1"/>
<Button HorizontalAlignment="Stretch" Margin="38,70,65.7200012207031,88.0400009155273" VerticalAlignment="Stretch" Content="Other Contents for this cell" Grid.Column="1"/>
<Button HorizontalAlignment="Stretch" Margin="38,70,65.7200012207031,88.0400009155273" VerticalAlignment="Stretch" Content="Other Contents for this cell" Grid.Row="1" Grid.Column="1"/>
</Grid>
</Border>
shanaolanxing - Please mark the posts as answers if they help and unmark if they don't.