Generic Multi-Select MVVM ListBox Drag and Drop Helper with Custom Feedback for Silverlight 4.0

<UserControl 
    x:Class="SL_MVVM_DragDropHelper_Sample.Views.Products"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
    xmlns:cmd="clr-namespace:GalaSoft.MvvmLight.Command;assembly=GalaSoft.MvvmLight.Extras.SL4"  
    DataContext="{Binding Path=Main, Source={StaticResource Locator}}"
    mc:Ignorable="d"
    >

    <UserControl.Resources>
        <DataTemplate x:Key="ProductModelTemplate">
            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="30"/>
                    <ColumnDefinition Width="80"/>
                    <ColumnDefinition Width="50"/>
                    <ColumnDefinition Width="50"/>
                </Grid.ColumnDefinitions>
                <TextBlock Text="{Binding product_id}"/>
                <TextBlock Grid.Column="1" Text="{Binding title}" TextTrimming="WordEllipsis"/>
                <TextBlock Grid.Column="2" Text="{Binding tags.Count}" TextAlignment="Right"/>
                <TextBlock Grid.Column="3" Text="{Binding group.group_id}" TextAlignment="Right"/>
            </Grid>
        </DataTemplate>
    </UserControl.Resources>

    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="20"/>
            <RowDefinition Height="20"/>
            <RowDefinition />
        </Grid.RowDefinitions>

        <StackPanel Orientation="Horizontal" HorizontalAlignment="Center" >
            <TextBlock Text="Products" TextAlignment="Center" Margin="4,0" FontWeight="Bold"/>
            <TextBlock Text="{Binding Products.Count, StringFormat='(\{0\})'}"/>
        </StackPanel>
        <Border Grid.Row="1" VerticalAlignment="Center" Background="#3D0000FF" >
            <Grid Margin="6,0,0,0">
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="30"/>
                    <ColumnDefinition Width="80"/>
                    <ColumnDefinition Width="50"/>
                    <ColumnDefinition Width="50"/>
                </Grid.ColumnDefinitions>
                <TextBlock Grid.Column="0" Text="ID"/>
                <TextBlock Grid.Column="1" Text="Title"/>
                <TextBlock Grid.Column="2" Text="Tags" TextAlignment="Right"/>
                <TextBlock Grid.Column="3" Text="Group" TextAlignment="Right"/>
            </Grid>
        </Border>
        <ListBox Name="lbProducts" Grid.Row="2" SelectionMode="Extended"
                 ItemsSource="{Binding Products}"
                 ItemTemplate="{StaticResource ProductModelTemplate}">
            <i:Interaction.Triggers>
                <!-- Trigger for Start Drag (LeftMouseDown does not fire). -->
                <i:EventTrigger EventName="MouseMove">
                    <cmd:EventToCommand Command="{Binding ProductsDragDropHelper.ChildMoveCommand, Mode=OneWay}"
                                        PassEventArgsToCommand="True" />
                </i:EventTrigger>
            </i:Interaction.Triggers>
        </ListBox>
    </Grid>

</UserControl>