Tags: , , , , , , , , , , , , , , , | Categories: Development Posted by bsstahl on 6/30/2015 4:45 AM | Comments (0)

In the last episode of “Refactoring my App Development Mojo”, I explained how I had discovered my passion for building Windows Store applications by using a hybrid solution of HTML5 with very minimal JavaScript, bound to a view-model written in C# running as a Windows Runtime Component, communicating with services written in C# using WCF.  The goal was to do as much of the coding as possible in the technologies I was very comfortable with, C# and HTML, and minimize the use of those technologies which I had never gotten comfortable with, namely JavaScript and XAML.

While this was an interesting and somewhat novel approach, it turned out to have a few fairly significant drawbacks:

    1. Using this hybrid approach meant there were two runtimes that had to be initialized and operating during execution, a costly drain on system resources, especially for mobile devices.

    2. Applications built using this methodology would run well on Windows 8 and 8.1 machines, as well as Windows Phone devices, but not  on the web, or on Android or iDevices.

    3. The more complex the applications became, the more I hand to rely on JavaScript anyway, even despite putting as much logic as possible into the C# layers.

      On top of these drawbacks, I now feel like it is time for me to get over my fear of moving to JavaScript. Yes, it is weakly typed (at least for now). Yes, its implementation of many object-oriented concepts leave a lot to be desired (at least for now), yes, it can sometimes make you question your own logical thinking, or even your sanity, with how it handles certain edge-cases. All that being said however, JavaScript, in some form, is the clear winner when it comes to web applications. There is no question that, if you are building standard front-ends for you applications, you need JavaScript.

      So, it seems that it is time for me to move to a more standard front-end development stack.  I need one that is cross-platform, ideally providing a good deployment story for web, PC, tablet & phone, and supporting all major platforms including Android, iDevices & Windows phones and tablets.  It also needs to be standards-based, and work using popular frameworks so that my apps can be kept up-to-date with the latest technology.

      I believe I have found this front-end platform in Apache Cordova. Cordova takes HTML5/JavaScript/CSS3 apps that can already work on the web, and builds them into hybrid apps that can run on virtually any platform including iPhones and iPads, Android phones and tablets, and Windows PCs, phones and tablets. Cordova has built-in support in Visual Studio 2015, which I have been playing with for a little while and seems to have real promise.  There is also the popular Ionic Framework for building Cordova apps which I plan to learn more about over the next few weeks.

      I’ll keep you informed of my progress and let you know if this does indeed turn out to be the best way for me to build apps. Stay tuned.

      Tags: , , , , , , , , | Categories: Development Posted by bsstahl on 6/28/2013 1:05 AM | Comments (0)

      On at least 2 occasions recently, I have heard speakers tell their audience that you cannot reference a target-specific .NET library (such as a .NET Framework 4.5 library) from a Portable Class Library. While this is technically true, it doesn't tell nearly the whole story. Even though we can't reference target-specific libraries, we can still USE these libraries. We can call their methods and access their properties under the right circumstances. We can gain access to these libraries via an abstraction. My preferred method of doing this is known as Dependency Injection.

      I'm going to give some quick background on PCLs and DI before getting into the details of how they can be used in this context. If you are familiar with Dependency Injection and .NET Portable Class Libraries you can skip these sections.

      .NET Portable Class Libraries (PCLs)

      Portable Class Libraries are .NET assemblies designed to be used by multiple target platforms in the .NET application space. You can specify which targets you want to be able to use, such as .NET 4.5, Silverlight 4, Windows Phone 8, etc. The compiler then does the work to limit the APIs you have at your disposal in that library to only the intersection of all of the selected targets. This guarantees that any code written in that library will work in all of those targets, but no target-specific (device-specific) functionality will be available. These libraries are great for business-logic and other platform-independent services but are not useable for code that requires direct access to device features like the UI, camera, GPS, etc. This code can be compiled and tested once, and then accessed from any of the selected target contexts.

      Dependency Injections (DI)

      Dependency Injection is a way of maintaining loose-coupling between application components. Instead of having a piece of code have a direct knowledge of one of its dependencies, the code only has knowledge of an abstraction of that dependency, usually an interface. Since the client is unaware of the implementation and only has knowledge of the abstraction, the implementation of the dependency can change, and as long as it maintains compliance to the interface, the client code is unaware of the change and continues to function normally. The correct dependency must then be "injected" into the calling code prior to being used. The client only knows that the dependency implements the needed interface, but is unaware of the actual implementation. This becomes extremely useful in unit-testing since a fake dependency such as a mock data-provider can be injected by the test context, allowing the tests to focus on the layer being tested without having to test the dependencies as well. While this is not nearly the only reason to use DI, it is an example of an excellent benefit of its use.

      Injecting Target-Specific Code into PCLs

      Let's suppose we have a .NET Portable Class Library that implements the business logic of our application. We want the application to be able to run on the web under ASP.NET, on Windows 8 as a Modern Windows Store App, and on Windows Phone 8. We built the PCL using these specific targets so we know (the compiler guarantees) that this code will run in any of those platforms. However, this code needs to get its data from somewhere, and that somewhere is different depending on what environment we are running in. In ASP.Net for example, we may want to get the data from Session State, or from a back-end SQL Server, while in Windows Phone 8 and Windows 8 we want to use their (different) implementations of isolated storage. We can accomplish this by defining an interface that is usable by all 3 targets in a PCL. We can then create our 3 different implementations of the storage library using target-specific code and inject the appropriate one into the constructor of one or more of the classes in the business-logic PCL. This injection can be done directly by the parent application, which is going to be target-specific so it would have knowledge of which target is needed, or it can be done indirectly using a DI Container such as Microsoft Unity.

      A sample app that is available in the 3 targets previously described may look something like this. The business-logic and domain layers (interfaces, exceptions, entities, etc) are both PCLs and exist for use in all 3 targets. The UI layer and Infrastructure layers (in this case, storage) are target-specific and require a separate implementation for each target platform. A system designed in this way can maximize the use of common, shared code while still making platform specific features available in a type-safe way.

      If you are interested in seeing this implementation done live, you can come to one of my Code Camp talks on the subject, or request me as a speaker for your User Group via Ineta.

      Tags: , , , , , , , , , , , , | Categories: Development Posted by bsstahl on 2/28/2013 6:34 PM | Comments (0)

      or, How I found my Passion for Windows 8 Store App Development

      Update: My first Windows Store app was published on March 27, 2013 and can be found here.

      I don't have any apps in the Windows 8 Store yet. For that matter, I don't have any apps in the Windows Phone store, or the Apple or Android stores either. I have many ideas for apps, and a number of them in the works for both Windows 8 and Windows Phone, but I have nothing real to show for it yet. Nothing to show for several years of attending sessions at conferences, user groups, and code camps on building these apps; for many hours of hacking on front-end interfaces and business logic. Don’t get me wrong, I've wanted to build these apps, but I didn't have that burning desire that I usually get when I am solving problems with software. You know that desire, the one that compels you to sit in front of a computer for hours at a time until you've completed a solution. I didn't have it.

      This recently changed for me -- let me explain.

      I have spent most of the last 20 years building enterprise web applications that do most of the work on the server side. My user interfaces have been built in HTML, with some JavaScript for validation and Ajax for dynamic post-backs, but all business rules were housed entirely on the server in either C#, VB or something similar. Even before .NET, in the classic ASP days, my logic executed on the server with VBScript calling components created in Visual Basic. Before that, it was Pascal programs spitting out pure HTML to the console which was then redirected to the browser stream by the web server. As a result, I am very comfortable with using HTML for layout, and multi-purpose languages like C# and VB.Net for the business logic and data access.

      In the app world however, this combination of technologies has seemed out-of-reach. In Windows Phone development, I could use C#, but needed to use XAML for layout and style, a technology that I have not yet been able to get comfortable with. For Windows 8 store apps there are more options, including HTML5/JavaScript apps, but I have never been comfortable writing code in JavaScript. The advent of TypeScript has brought us even closer to a solution in my comfort zone where I can get almost a C# style experience with HTML5 as my layout mechanism, but I am still missing key features like LINQ and generics.

      Enter Windows Runtime Components. I say “enter”, as if they were new -- they're not, I just apparently allowed myself to forget about them. RT Components can be written in C# (and other languages), but can be called from JavaScript or any Windows 8 Store code, just as if they were written in that same language. RT components can also call into any .NET code that can be executed in a Windows Store App. As a result, I have the power of C# and the .NET Framework at my disposal while writing a JavaScript app. All I have to do is wrap my .NET Windows Store compatible libraries in an RT component, and use JavaScript to bind it to my HTML layout. Since I have been using Portable Libraries for most of my business logic for some time now, and those libraries that aren't yet portable, are generally easily translated, most of my .NET business logic is already available for me to wrap in an RT Component.

      With the primary business functionality done in C#, it becomes a relatively trivial exercise in JavaScript to bind my RT model to the HTML components in my UI. This experience is completely comfortable to me, and in using this process, I have found the passion I was missing for building these apps. I will have several apps in the Windows 8 store in the next few weeks with more to follow after that. I will also be writing about my methods in building these apps, from the perspective of an enterprise developer. Hopefully, this will allow others to find the passion for creating these apps as I have. In the meantime, here are a few tips you can start using now to ease the transition into building apps:

      1. Use portable libraries wherever possible, especially for business logic.
      2. Use dependency injection to make non-portable dependencies available to portable libraries. This will allow your business logic access to platform-specific functionality (such as network access) without sacrificing portability.
      3. Do as much of the work as possible in the underlying .NET libraries and keep the RT Component as thin a translation layer as possible. I will be exploring techniques for this in the near future. Possibilities here include making this layer either a View-Model or a Repository implementation.
      4. The only logic in the JavaScript code should be that which is required to bind the RT Component to your controls. If you are doing more than setting event handlers and other control properties in your JavaScript, you might want to think about moving that functionality into a lower layer. This has the added benefit of making that logic potentially reusable across applications.

      I’m interested to hear if there are other enterprise developers with similar stories, whose comfort zones of HTML and C# or VB have kept them from building apps as they’d like. Please contact me on Twitter at @bsstahl.