I’ve given a lot of thought over the past few weeks to application migration scenarios.  I did a lot of this with the cloud when Windows Azure first launched in 2009, doing a number of blog posts and presentations about moving ASP/.NET code to the cloud.  Now, I’ve been thinking more about moving applications to Windows 8, and given the choices and frameworks available today, I’m often asked what I would do in various situations.  Let’s start with an overview of Windows 8, using this graphic from \\build that you’ve likely seen before:

I originally intended this post to be about MVVM, the Model-View-ViewModel design pattern that everyone loves, but few actually use.   It’s not because people think they’re doing MVVM but really not (although I hear this one a lot, too), it’s just that very few greenfield apps are being built and even the ones that are are either 1) too simple to consider a design pattern, or 2) it’s sacrificed to get to production in the least amount of time.  I still believe creating testable, solid code around well principled design patterns (be it MVC, MVVM, or whatever) will yield the most benefit over the long term if there are anticipated modifications and maintenance needs.  But in the short term or for small projects, it’s typically not a benefit due to longer development time and performance tradeoffs.  (A few popular MVVM frameworks out there include Prism, MVVM Light, and Caliburn.Micro.)

While creating a write-once run anywhere app won’t happen (yet), you can reduce the friction as much as possible.  When moving to Windows 8 from Windows Phone, there are two primary objectives: adapt the UI, and change WP API calls to WinRT API calls.   Here’s a great article on MSDN with more info on that.   (Notice that one tip in the article is refactoring to MVVM.)

For line of business applications, Silverlight, or WPF migrations, XAML and C# offers the easiest migration and new development experience, and leveraging the above frameworks or MVVM pattern can make that transition as painless as possible.   If you’re lucky enough to do greenfield development where broad platform reach is the goal, there’s only 1 development choice:  HTML 5.   If you are a developer and not sold on the fact that HTML 5 is the development platform to know over the next 3 years (at a minimum), you need to embrace HTML 5. 

To that end, for Windows 8 development I’d start with frameworks like KnockoutJS (an open source, Javascript-based MVVM engine) and this post written by Dave Isbitski, my colleague.    It’s also a good idea to look into PhoneGap, Sencha Touch 2, and KendoUI.

In the next post along these lines, we’ll look into specific frameworks and integrating them into Win8 apps.

Link roundup:

\\build

MVVM, the Model-View-ViewModel design pattern

Prism

MVVM Light

Caliburn.Micro

MSDN:  Windows Phone to Windows 8 Migration

KnockoutJS

Dave Isbitski - KnockoutJS and Windows 8

PhoneGap

Sencha Touch 2

KendoUI