Q:

adding eventsetter for datarow not firing

Inside of app.xaml I have datagrid style
and for each window that contains a datagrid, I added an event setter for the datagridrow.
however, when I run it, I can see the style, but when I try to trigger the event nothing happens. if I remove the style from app.xaml. the event works well.
why app.xaml style disable my eventsetter?
here's the datagrid inside the app.xaml:
<Style TargetType="DataGrid">
        <Setter Property="Background" Value="Transparent"/>
        <Setter Property="HorizontalAlignment" Value="Center"/>
        <Setter Property="BorderThickness" Value="0"/>
        <Setter Property="GridLinesVisibility" Value="None"/>
        <Setter Property="BorderBrush" Value="Transparent"/>
        <Setter Property="RowStyle">
            <Setter.Value>
                <Style TargetType="DataGridRow">
                    <Setter Property="Background" Value="Transparent"/>
                    <Setter Property="HorizontalAlignment" Value="Center"/>
                    <Setter Property="Foreground" Value="White"/>                        
                </Style>
            </Setter.Value>
        </Setter>
        <Setter Property="ColumnHeaderStyle">
            <Setter.Value>
                <Style TargetType="DataGridColumnHeader">
                    <Setter Property="Margin" Value="5,0,0,0"/>
                    <Setter Property="Foreground" Value="White"/>
                    <Setter Property="Background" Value="Transparent"/>
                    <Setter Property="Template">
                        <Setter.Value>
                            <ControlTemplate TargetType="{ x:Type DataGridColumnHeader}">
                                    <Border BorderThickness="2,2,2,0" CornerRadius="5,5,0,0">
                                    <Border.Style>
                                        <Style TargetType="Border">
                                            <Setter Property="BorderBrush" Value="White"/>
                                            <Style.Triggers>
                                                <DataTrigger Binding="{Binding Path=Content, RelativeSource={RelativeSource TemplatedParent}}" Value="{x:Null}">
                                                    <Setter Property="BorderBrush" Value="Transparent"/>
                                                </DataTrigger>
                                            </Style.Triggers>
                                        </Style>
                                    </Border.Style>
                                    <ContentPresenter HorizontalAlignment="Center" Margin="5"></ContentPresenter>
                                    </Border>
                            </ControlTemplate>
                        </Setter.Value>
                    </Setter>
                </Style>
            </Setter.Value>
        </Setter>
    </Style>

here's the eventsetter inside each window that contains datagrid:
<Style TargetType="DataGridRow">
        <EventSetter Event="MouseDoubleClick" Handler="EditItem"/>
    </Style>

A:

It seems, that the grid uses the RowStyle from it's property later, than it has been set in window's resources. It will work, if you clear your RowStyle property in grid. Put this to the window's resources:  
<Style TargetType="DataGrid" BasedOn="{StaticResource {x:Type DataGrid}}">
    <Setter Property="RowStyle" Value="{x:Null}"/>
</Style>

For you can use the style set in app.xaml, you have to move the RowStyle from property to global(in app.xaml):  
    <Style TargetType="DataGrid">
....
                <Setter Property="RowStyle" Value="{x:Null}"/>
...
            </Style>

<Style TargetType="DataGridRow" BasedOn="{StaticResource {x:Type DataGridRow}}">
    <Setter Property="Background" Value="Green"/>
    <Setter Property="HorizontalAlignment" Value="Center"/>
    <Setter Property="Foreground" Value="White"/>
</Style>

and in window's resources:  
<Style TargetType="DataGridRow" BasedOn="{StaticResource {x:Type DataGridRow}}">
                        <EventSetter Event="MouseDoubleClick" Handler="PreviewMouseDown"/>
                    </Style>

