Sample ListBox (XAML) where Drag originates:

<ListBox Name="lstEnvironments" 
               SelectionChanged="lstEnvironments_SelectionChanged" 
               PreviewMouseLeftButtonDown="lstEnvironments_PreviewMouseLeftButtonDown" 
               MouseMove="lstEnvironments_MouseMove">
          <ListBoxItem>Normal</ListBoxItem>
          <ListBoxItem>Restaurant/Party</ListBoxItem>
          <ListBoxItem>Telephone</ListBoxItem>
          <ListBoxItem>Music</ListBoxItem>
</ListBox>

Target controls where Drop is performed. In this case, a ListBox, TextBlock, and TextBox.

<TextBlock FontWeight="Bold" Margin="0,10,0,0">Dragged Items</TextBlock>
<TextBlock>ListBox:</TextBlock>
<ListBox Name="lstAppliedEnvironment" AllowDrop="True" Height="100"  SelectionMode="Single"
         DragEnter="lstAppliedEnvironment_DragEnter"
         Drop="lstAppliedEnvironment_Drop">
    <!--<ListBoxItem>Empty</ListBoxItem>-->
</ListBox>
<StackPanel Orientation="Horizontal">
    <TextBlock>TextBlock:</TextBlock>
    <TextBlock Name="lblAppliedEnvironment" Margin="5,0,0,20" AllowDrop="True"
           DragEnter="lblAppliedEnvironment_DragEnter" Drop="lblApliedEnvironment_Drop">Value</TextBlock>
</StackPanel>
<TextBox Name="txtAppliedEnvironment"  Height="30" AllowDrop="True" 
         DragEnter="txtSelectedEnvironment_DragEnter" 
         Drop="txtAppliedEnvironment_Drop">Test 2</TextBox>

• Drag and Drop in WPF
• Drag and Drop in WPF Explained End to End
• MSDN: Drag and Drop Overview
• WPF Tutorial: Drag and Drop