Different look in design-mode and at runtime - wpf

Question

I have small problem with WPF.
Here is my Style where I created a template for DataGrid Column Header.
<Window.Resources>
<Style x:Key="DataGridColumnHeaderStyle1" TargetType="{x:Type DataGridColumnHeader}">
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type DataGridColumnHeader}">
<Grid>
<Microsoft_Windows_Themes:DataGridHeaderBorder BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" IsClickable="{TemplateBinding CanUserSort}" IsPressed="{TemplateBinding IsPressed}" IsHovered="{TemplateBinding IsMouseOver}" Padding="{TemplateBinding Padding}" SortDirection="{TemplateBinding SortDirection}" SeparatorBrush="{TemplateBinding SeparatorBrush}" SeparatorVisibility="{TemplateBinding SeparatorVisibility}">
<Microsoft_Windows_Themes:DataGridHeaderBorder.Background>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#FF7EE4FF" Offset="0"/>
<GradientStop Color="#FF66D6F3" Offset="1"/>
<GradientStop Color="#FF0097BE" Offset="0.5"/>
</LinearGradientBrush>
</Microsoft_Windows_Themes:DataGridHeaderBorder.Background>
<ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
</Microsoft_Windows_Themes:DataGridHeaderBorder>
</Grid>
</ControlTemplate>
</Setter.Value>
Here's my DataGrid view control in Grid:
<DataGrid Margin="46.667,41.333,102,87">
<DataGrid.Columns>
<DataGridTemplateColumn Header="Status" Width="*" HeaderStyle=" {DynamicResource DataGridColumnHeaderStyle1}"/>
</DataGrid.Columns>
</DataGrid>
The problem is I can see modified header in VS designer, or in Blend, but when I run my application header style is default. Can anyone help? Thanks in advance.
EDIT
Just found interesting thing. When I put Style in
DataGridTemplateColumn.HeaderStyle
it's working
<DataGrid Margin="46.667,41.333,102,87">
<DataGrid.Columns>
<DataGridTemplateColumn Header="Status" Width="*">
<DataGridTemplateColumn.HeaderStyle>
<Style TargetType="{x:Type DataGridColumnHeader}">
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type DataGridColumnHeader}">
<Grid>
<Microsoft_Windows_Themes:DataGridHeaderBorder BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" IsClickable="{TemplateBinding CanUserSort}" IsPressed="{TemplateBinding IsPressed}" IsHovered="{TemplateBinding IsMouseOver}" Padding="{TemplateBinding Padding}" SortDirection="{TemplateBinding SortDirection}" SeparatorBrush="{TemplateBinding SeparatorBrush}" SeparatorVisibility="{TemplateBinding SeparatorVisibility}">
<Microsoft_Windows_Themes:DataGridHeaderBorder.Background>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#FF7EE4FF" Offset="0"/>
<GradientStop Color="#FF66D6F3" Offset="1"/>
<GradientStop Color="#FF0097BE" Offset="0.5"/>
</LinearGradientBrush>
</Microsoft_Windows_Themes:DataGridHeaderBorder.Background>
<ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
</Microsoft_Windows_Themes:DataGridHeaderBorder>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</DataGridTemplateColumn.HeaderStyle>
</DataGridTemplateColumn>
</DataGrid.Columns>
</DataGrid>
Why does it make a difference?

Answer 1

It looks like the DynamicResource is not resolving correctly at runtime. Try switching your DynamicResource to a StaticResource like so:
<DataGridTemplateColumn Header="Status" Width="*"
HeaderStyle="{StaticResource DataGridColumnHeaderStyle1}"/>
For more details on the differences between DynamicResource and StaticResource, see this other StackOverflow question: What's the difference between StaticResource and DynamicResource in WPF?