Read original post by Usman Ur Rehman Ahmed at Microsoft Pakistan Community Blog
Probably the idea of drag and drop are at the heart of educational, children learning and quiz sort of apps. Since I’m often contacted on how to achieve drag and drop using Silverlight for Windows Phone, I thought to write a basic blog post covering this aspect.
The first thing you need to understand is that you need to write custom code to handle your particular scenario. Please note that implementation provided below serves only a starting note and that it makes use of Microsoft.XNA.Framework DLL to make collision detection and location tracking easier (using built in Rectangle and Vector2 classes in XNA).