WPF从列表框拖动元素

在我的WPF应用程序中，我有一个列表框，其中的DataTemplate定义如下：

 <DataTemplate x:Key="ListBoxTemplate">
            <ui:TaskMonthPreview/>
 </DataTemplate>

<UserControl x:Class="Lista.TaskMonthPreview"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Height="30" Width="100">

    <UserControl.Resources>
        <ResourceDictionary>
            <ControlTemplate x:Key="TaskView" TargetType="Thumb">

                <Rectangle
                Name="rectangle1" 
                Stroke="Chocolate" 
                HorizontalAlignment="Left" 
                Width="{TemplateBinding Width}" 
                Height="{TemplateBinding Height}" 
                Fill="LightSkyBlue"/>

            </ControlTemplate>
        </ResourceDictionary>
    </UserControl.Resources>



        <Thumb Name="myThumb"  Background="Blue" 
          Width="100" Height="20" DragDelta="onDragDelta" 
          DragStarted="onDragStarted" DragCompleted="onDragCompleted" HorizontalAlignment="Left"
          Template="{StaticResource TaskView}"/>



</UserControl>

TaskMonthPreview是我的自定义控件，定义如下：

 <DataTemplate x:Key="ListBoxTemplate">
            <ui:TaskMonthPreview/>
 </DataTemplate>

<UserControl x:Class="Lista.TaskMonthPreview"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Height="30" Width="100">

    <UserControl.Resources>
        <ResourceDictionary>
            <ControlTemplate x:Key="TaskView" TargetType="Thumb">

                <Rectangle
                Name="rectangle1" 
                Stroke="Chocolate" 
                HorizontalAlignment="Left" 
                Width="{TemplateBinding Width}" 
                Height="{TemplateBinding Height}" 
                Fill="LightSkyBlue"/>

            </ControlTemplate>
        </ResourceDictionary>
    </UserControl.Resources>



        <Thumb Name="myThumb"  Background="Blue" 
          Width="100" Height="20" DragDelta="onDragDelta" 
          DragStarted="onDragStarted" DragCompleted="onDragCompleted" HorizontalAlignment="Left"
          Template="{StaticResource TaskView}"/>



</UserControl>

我在TaskMonthPreview中的拇指是可拖动的，但不幸的是，它不能拖动到TaskMonthPreview区域之外。是否可以将我的拇指拖动到TaskMonthPreview范围之外，甚至listbox范围之外