what is the best practice to implement an update ability (partial update may be) [on hold]

I want to develop my desktop application in a way that makes me able to provide update packages like visual studio does; in this way user shouldn't download the whole application and install it again to update just a bit of it.

to make it clear, I need some advice to guide me to the right direction, for example:

• should I separate my application in to a lot of projects (.dll) to provide a partial update or what?
• is there a specific design pattern or library or what ever that help me not to start from scratch?

I use C#, Wpf, Prism, and application has no database, it's just about some processing and presenting result to the user.