How to apply nested Styles from ResourceDictionary in WPF? - wpf

Question

I use a DataGrid (WPF 4.0) control. The style for it is placed in a ResourceDictionary and contains a nested Style element:
<Style x:Key="MyDataGridStyle" TargetType="{x:Type controls:DataGrid}">
<Setter Property="Background" Value="Black"/>
<Setter Property="CellStyle">
<Setter.Value>
<Style TargetType="{x:Type DataGridCell}">
<Setter Property="BorderThickness" Value="0" />
<Setter Property="FocusVisualStyle" Value="{x:Null}" />
</Style>
</Setter.Value>
</Setter>
</Style>
Here, only the Background style is applied. The CellStyle NOT.
It only works when I define the CellStyle directly inside the DataGrid element:
<DataGrid Style="{StaticResource MyDataGridStyle}">
<DataGrid.CellStyle>
<Style TargetType="{x:Type DataGridCell}">
<Setter Property="BorderThickness" Value="0" />
<Setter Property="FocusVisualStyle" Value="{x:Null}" />
</Style>
</DataGrid.CellStyle>
</DataGrid>
Any ideas why?
Update
It seems that there is a problem when mixing styles with PresentationFramework.Aero theme that I have referenced in my ResourceDictionary. If I remove the reference it works!

Answer 1

Doing it the way you suggest works fine for me, I'll paste the code that I used to test your style. (note that I added background = red so I could actually see if the style was being applied)
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<Style x:Key="MyDataGridStyle" TargetType="{x:Type DataGrid}">
<Setter Property="Background" Value="Black"/>
<Setter Property="CellStyle">
<Setter.Value>
<Style TargetType="{x:Type DataGridCell}">
<Setter Property="BorderThickness" Value="0" />
<Setter Property="Background" Value="Red"/>
<Setter Property="FocusVisualStyle" Value="{x:Null}" />
</Style>
</Setter.Value>
</Setter>
</Style>
</Window.Resources>
<DataGrid Style="{StaticResource MyDataGridStyle}">
<DataGrid.Columns>
<DataGridTextColumn Binding="{Binding Text}"/>
<DataGridTextColumn Binding="{Binding Tag}"/>
</DataGrid.Columns>
<DataGrid.Items>
<TextBlock Text="Item1" Tag="aa"/>
<TextBlock Text="Item2" Tag="bb"/>
<TextBlock Text="Item3" Tag="cc"/>
<TextBlock Text="Item4" Tag="dd"/>
</DataGrid.Items>
</DataGrid>
</Window>
the results are