Draggable Popup Window in Silverlight 3

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Introduction

In Silverlight 3, you can use a Popup control to show a non-modal window containing any sort of content. Although you can control the Popup's position by setting the HorizontalOffset and VerticalOffset properties, it can sometimes be hard to predict where the user would like the window to be positioned. Unfortunately, the user has no way to move the Popup control.

By attaching a PopupDragDrop object to your Popup control, you allow the user to drag it around the Silverlight window and place it wherever she likes.

Using the code

Simply call the static PopupDragDrop.Attach method to wire up an instance of the class to your Popup. Attach takes two arguments: the Popup control and the FrameworkElement that will be the Popup's child (which holds the actual content that will be displayed). For example:

// Create the Popup control and set the initial position.	
Popup myPopup = new Popup { HorizontalOffset = 200, VerticalOffset = 300 };

// Attach a PopupDragDrop object to make your Popup draggable.
// The Attach method will also set the Child property of the Popup.
PopupDragDrop.Attach(myPopup, new myUserControl());

From this point, you show/hide the Popup in the usual way, using the IsOpen property of the Popup and the Visibility property of the child.