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Welcome to the second part of this article series on what’s new in the Windows 8.1 update for developers. In the first part, we’ve spent some time looking at the new features, mostly from an end-user’s perspective. We haven’t seen any code yet. That’s about to change with this second part.

The goal of this article is showing you the new stuff in XAML and WinRT. The WinRT library has been extended with a great deal of extra classes and features that allow compelling experiences. Part of all that is of course XAML, in which a huge number of extra controls has been added.

Hi and welcome to a new series of articles here on SIlverlightShow where we will give an overview of the new concepts and changes in the first big update of Windows 8, known to mankind as Windows 8.1. Over the next couple of articles, we will take a look at the things that have changed. You’ll soon understand that while the changes you’ll have to do in your code are often subtle, they will lead to a much better user experience which is in-line with the new version of the OS.

In this first part, we are going to introduce the new version and see what has changed.

In the previous article I've talked about the basic location api and I've introduced the geo-fencing features that are new in Windows 8.1. These API, partly already available in the very first release of the operating system, are for sure a interesting opportunity to build location aware applications, taking the full advantage from the "mobility" of modern devices. The API that I've explained, are all made to be used when you application is running, but as you probably figured out, this is not exactly the most common situation for our applications.

Mobile devices have grown a lot in the last years and a lot of practical applications are developing a huge market around them. One of the most important points that made the success of mobile devices is the availability of sensor that uses the Global Positioning System (GPS) to detect the geographic location of the devices. GPS Sensor is supported in Windows Store apps since the very first release but it has got a number of new and important features that maximizes the capabilities of your device giving new horizons to your ideas.

As often happens, the timeframe passed between the release of Windows 8 and the new release numbered 8.1, have brought to the light some things that developers felt missing during the their work. Many of these are simply obvious features left behind just for time issues, others are answers to new needs that could not be imagined in the first release, and others again are some effective behaviors proposed by some successful application. In this release all these paradigms have created a new output, in the form of a number of "Controls" that are now available to developers.

After the last article where I spoken about the use of behaviors in Windows 8.1, it is time now to go deep inside the SDK and try to create our own behaviors. The SDK in Windows 8.1 includes a number of predefined behaviors that out-of-the box cover a number of cases, both with different activations (event driven and data driven) and with a number of actions, from the simplest property change to the manipulation of states and the invocation of commands. Connecting together predefined activation behaviors and actions suffice for most of the problems you may meet during development, but there are cases when only a specifically-tailored logic can solve an hassle.

Together with Silverlight 3.0 RTM, hidden inside the release of Blend 3.0 in later 2009, Microsoft released an interesting feature that in the projects had to support Sketckflow users. These small pieces of codes, at the first sight appeared as a "draggable" logic, made to increase the designers productivity by adding specific behaviors to objects, directly from the design surface. The "behaviors", this is the name given to these new elements, were part of the Blend 3.0 SDK as a separate download and this contributed to them success.

In my last article I showed a simple example about the organization of the UI layer using Model View ViewModel in XAML. There is not any doubt that this pattern is a great help to make the application more maintainable, thanks to the effective separation between logic and views. MVVM is born with XAML, but after you embraced its power, it is hard to give up and return to the previous ways to develop applications. So my question is: "is it possible to apply the same pattern outside of XAML, also in an HTML5 app?" The first and evident obstacle to this achievement is the complete lack of databinding in Javascript and additionally the lack of some tools, like observables types, that directly feed the pattern.

Having a deep knowledge of your toolset, when you start a new application from scratch, does not necessarily mean you are able to develop rapidly and effectively. The biggest problems, infact, do not come from the missing knowledge of a feature, that you can easily fill with a short search on the Internet, but from the grow of complexity of your application when you start putting things together without knowing exactly how you can better organize them to avoid the exponential increase of entropy.