change datagrid row template dynamicly
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I'm building wpf application. 

Here is my data grid:

       <controls:McaDataGrid x:Name="dgFormTable" Style="{StaticResource FormTableDataGridStyle}" 
                                                  CanUserAddRows="False" CanUserReorderColumns="False" CanUserResizeColumns="False"
                                                  IsReadOnly="True" AutoGeneratingColumn="dgFormTable_AutoGeneratingColumn"
                                                  RowStyleSelector="{DynamicResource dgFormTableRowStyleSelector}"
                                                  HorizontalScrollBarVisibility="Disabled" VerticalScrollBarVisibility="Disabled"
                                                  LoadingRow="dgFormTable_LoadingRow"
                                                  Width="{Binding ElementName=borDataGridContainer, Path=ActualWidth}"
                                                  />

and here is the style:

    <Style TargetType="{x:Type toolkit:DataGrid}" x:Key="FormTableDataGridStyle" BasedOn="{StaticResource BaseDataGridStyle}">
		<Setter Property="HeadersVisibility" Value="Column"/>
		<Setter Property="BorderThickness" Value="0"/>
		<Setter Property="Background" Value="Transparent"/>
		<Setter Property="GridLinesVisibility" Value="Horizontal"/>
		<Setter Property="SelectionUnit" Value="Cell"/>
		<Setter Property="HorizontalGridLinesBrush" Value="{StaticResource GridHorizontalLineBrush}"/>
		<Setter Property="ColumnHeaderStyle" Value="{StaticResource FormTableColumnHeaderStyle}"/>
		<Setter Property="CellStyle" Value="{StaticResource FormTableCellStyle}"/>
		<Setter Property="ColumnWidth" Value="*"/>        
	</Style>

I have a helper class for selecting grid row styles, but background setter in only the one thing in that styles. The items of datagrid is enumerable collection of dynamic type, so I don't have "strongly typed" style for row.

Now I need to add to the bottom (or to the top) of some rows in this grid a line. This have to be done dynamicly on row loading. (i.e. need to add some element to some rows dynamicly)

Could anyone help me with this?