
Explanation/Reference:
Explanation:
Box 1: AllowDrop
Box 2: DragOver
Box 3: Grid_DragOver
Box 4: Drop
Use the AllowDrop and CanDrag properties to designate the areas of your app valid for dragging and dropping.
The following markup shows how to set a specific area of the app as valid for dropping by using the AllowDrop in XAML. If a user tries to drop somewhere else, the system won't let them. If you want users to be able to drop items anywhere on your app, set the entire background as a drop target.
<Grid AllowDrop="True" DragOver="Grid_DragOver" Drop="Grid_Drop"
Background="LightBlue" Margin="10,10,10,353">
<TextBlock>Drop anywhere in the blue area</TextBlock>
</Grid>
Reference: https://docs.microsoft.com/en-us/windows/uwp/app-to-app/drag-and-drop