Seeing as how MVVM is being highly regarded as a good system design pattern, I thought I might just jump aboard and give MVVM a shot.
Just a little background about myself before I begin with questions:
I have done a few years of development with ASP.NET Webforms. I have also done a fair bit of development in ASP.NET MVC, which I am quite comfortable with.
Currently, we have a number of "backbone" applications written using ASP.NET MVC 3 which we customize and sell to our clients whenever we're approached. These applications are all meant for internal use, hence plug-ins wouldn't be much of a problem.
The real problem with development is that for large scale business applications with complex business rules, ASP.NET MVC tends to slow us down (writing jQuery / javascript > server side processing > return result, use jQuery to notify > alter view, something along this line).
Then I began looking for answers that will help us improve our time to delivery and also responsiveness (well, we all know how JavaScript is capable of killing us) and my search brought me to Silverlight (we have the time to change, no worries there).
So here comes the questions:
I have come across many Silverlight MVVM samples online, but all of them show applications as simple as interacting with only one Database table. Is MVVM pattern well suited for large applications?
In MVC, I'm used to Dependency Injection from Ninject to pass an implementation of UnitOfWork to my Controller. In all samples I found online, none of them use any form of DI. Is it really unnecessary? Since the idea of MVVM is to decouple, so why not also decouple ViewModel from Model?
I've gone through a book published by Jeremy Likness called Designing Silverlight Business Applications. He used MEF to do the decoupling, which I think doesn't really fit into our application. We do not really need to do "hot-plugging". What's your take on this?
MVVM is all about Commands, Databindings and No Code-behinds. What if I want to interact with UIs that do not expose to commands? (I'm not too sure about this, I'm guessing ListView OnSelectionChange?)
To add to the previous answer:
We are developing a large corporate-wide Silverlight platform and a set of applications using MVVM. Seems to be working pretty well.
We are using DI extensively. Our system is built on top of Prism. Prism contains a large amount of sample applications of various complexity illustrating the use of DI in MVVM.
We use Unity as our IoC container. Prism contains guidance for both MEF and Unity. Unity seems to be a more traditional IoC approach.
In the vast majority of cases using Bindings and Commands covered our needs. For the others we use Expression Triggers and Actions. You can also create custom Triggers/Actions if necessary.
I have no answers for all your answers (never used MEF) but I can tell you my experience:
1- I've been in the development of a quite-large silverlight application and MVVM fits perfect to have a maintainable application. The bigger problems we had because of application size were because of Silverlight, not MVVM 8-)
2- I haven't used it too much but it's useful in many cases. There are several toolkits to use DI with Silverlight like MVVM Light Toolkit:
http://compiledexperience.com/blog/posts/blendable-mvvm-dependency-injection-and-unit-testing
4- For interaction between UIs you can use the Mediator pattern. The same MVVM Light Toolkit has a Messenger to subscribe, send and receive messages and maitain every layer decoupled.
Hope this helps you ;-)
Related
We are in a process of technology selection for enterprise windows application and considering using WPF. We have decided to use WPF since The ability to make very rich UIs. Now the question is whether we should use MVVM or event (MVP). We are considering to use MVVM because.
Layered architecture.
Minimize duplicate code.
Testability.
Our team is well experience with ASP.net web form and MVC and most of us have web background. Some team members have little bit of windows form application development experience. I know it is little bit of learning curve to learn MVVM and Our architect wants to reuse code as much as possible. Our application is little bit complex and has lot of Grid control. Can someone please guide us regarding this matter? Should we stick in to MVVM or should we go ahead with event base wcf.
If MVVM is suitable for our application what would be the best MVVM Framework?
Please take a look at the recent MVVM advantage for freelancer developer? post. You will see that it has been put on hold because it is a subjective question, just like yours... this may happen to yours also.
I am going to develop a winform project of considerable size. I am planning to use Entity Framework as ORM tool. Now I am searching for an architecture(MVC/MVP/MVVM etc..) to implement all these. Firstly there are few choices for n-layered architecture for windows forms and most those I get are written prior to EF came into market. I got a framework called Rocket Framework from codeplex(http://rocketframework.codeplex.com)
I have looked around it but am skeptical that it will accommodate a wide range of requirements. If anyone has already discovered the wheel already, please guide me through.
Also if the existing architectures prior EF4 can accommodate it than also I can give it a try.
Ideas please!
Well your choices is influenced by the technology you're using. Some technologies make a certain pattern natural to do and thus if you (and every developer) don't explicitely design and care about this you'll end up with what feels most natural. On WinForms the most natural pattern is MVP. You have your view that you can layout in the designer and your code-behind file becomes the presenter, essentially combining view and presenter in one class (it's a 1:1 relationship anyway). For web applications on the other hand MVC is a natural pattern since your web server already acts as a controller. Finally MVVM is supported very well in WPF, although you could fall towards MVP there as well if you start using the code behind file a lot. But relying on DataBinding instead can make you forget to use the code behind file. A good article I read about this is here. Of course you can realize MVVM with WinForms, read this link for a good example.
From the point of testability MVVM is perceived as the best pattern since your view model (and therefor the behavior of your view) can be tested without an actual GUI. MVP however is easy to understand and realize, doesn't require complex bindings and gives you most control over what is happening (e.g. event suppression).
WinForms applications are mostly developed with MVP pattern. The original MVC is not used very much - only its Model-2 variant (for example ASP.NET MVC) for web applications. MVVM is used primarily with WPF and Silverlight.
Neither of these patterns affects how you use Entity framework - they are not data access related patterns.
After a lot of R&D and extensive study I finally settled here:
https://github.com/geersch/ModelViewPresenter
It is an MVP architecture written by Christophe Geers. It supports all I needed- Architecture for winform, web portability support, Entity Framework. Really nice and easy to use.
Additional reading:
http://www.cerquit.com/blogs/post/MVP-Part-I-e28093-Building-it-from-Scratch.aspx
We have lots of project developed using .net 2.0 version if I want to convert those project to WPF then what will be the approach. Please discuss in detail.
to let the migration to WPF easy, be sure that your existing code doesnt contains a high coupling between GUI and your Business layer, if it's the case the most important step is to refactor your existing code, so your GUI code will contains only what's related to GUI.
And after this step the part of your project to migrate will be not the big one, it will concerns only the GUI logic.
When I did this kind of migration from winform to WPF , we spent more time to remove coupling between GUI and other layers than to migrate the GUI layer, due to high coupling betwn GUI and other layers.
Having gone through a similar exercise I'll tell you that it can be done but there are some challenges.
Step1: Just for clarification when we say WPF some people mean Silvelright / web. WPF is not Silverlight so you need to clarify I want to migrate existing applicaitons to WPF thick client applications. Since you stated WPF I am assuming you mean thich client/windows based applications so we'll go that route. (I'll mention SL at the end)
Step 2: Evaluate your projects from the code level for the most part refactoring the code is fairly easy. Since you are migrating from .net 2.0 to .net 4.0 I would really look at how many of your classes are defined, and see what can be refactored or in some isntances completely redesigned. THis leads us directly into step 3.
Step 3: Pick a design pattern. One of the tricky parts is coming to terms with a new design patterns such as MVVM for WPF. More than lilkely you will want to strip out and redesign the entire UI. As a result you will also want to utilize a proper design pattern (MVVM) or some flavor of that. This will also tie back to step two as some of your code will need to change to support your design pattern.
There are a ton of resources online for MVVM as well as UI development. If you are looking for reading materials I would look to WPF 4 unleashed as well as WPF illustrated. Both are good reads to help you get up to speed on the UI components how they work and the proper approach to using them in a project.
Get familar with .net 4 and the use of collections, types and of course the numerous new classes for wpf.
Disclaimer: You can in many instances create a WPF application usign tradition winform layout and practices. Whether this is right or wrong is a matter of opion of the developer. My personal opinion is that yes you can forego learning new design patterns and use a winform approach but you will not gain the full benefit and capabilities of the framework using this approach.
And finally if you are planning to migrate these apps to the web (silverlight) your work will be a little more of a challenge. Silvelright does have a little higer learning curve and there are a few more rules (security, asynchronous calls, web services etc) that must be learned, and followed. I have foudn that in creating a migration that it is easier to migrate from Siverlight to WPF that vice versa. As Microsoft continues to improve Sivelright I think we will get to the point to where the code is interchangeable between the two patterns however right now it's not there.
Conduct a search online but here are a few links to help you get started:
Scott Guthrie (Silverlight) http://weblogs.asp.net/scottgu/default.aspx
Josh Smith (WPF MVVM) http://joshsmithonwpf.wordpress.com/
best of luck
I'm working on Silverlight, of course I use MVVM. I found many problems but I can create work-around solution for them (some of these solution is not elegant at all), now I think it's time to bring some framework to help me.
I need functions that listed below.
Dependency Injection
Navigation
Callback
Messaging
Bind event to Command
Testability
As I know, there are many Framework out there, such as, Jounce, MVVMLight and Prism. I want to know which framework is suitable for my need?
When it comes to dependency injection I'd rather use MEF
which greatly simplifies code. As for the rest of the functions , currently I'm working with MVVMLight and I haven't faced any problem (although I'm not familiar with Jounce and Prism)
I think that you should consider the scale of the application. If it is a relatively small application that is unlikely to grow I would choose MVVMLight.
For a larger LOB application I would consider PRISM or Caliburn. I would also recommend reading blog posts by John Papa and Jeremy MIller on MVVM, Screens and Coordinators. Their ideas and insights helped enormously in a large scale Silverlight project I've built.
In WPF Prism is great, in Silverlight Jounce is the best by far. Its is very well integrated with MEF , very lightweight, elegant and stable. It also provides nice implementation to support complex events workflow scenarios, VisualStateManager in ViewModel (love that one), validation, debugging and unit testing; Used it in some quite complex projects and was happy I chose it.
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So i decide to to develop my asp.net site into Silverlight.
I today start to search articles about MVVM pattern which i want use in my Silverlight app, and i am confused :/ It's hart to me understand how works this pattern. I am find 3 frameworks which supports MVVM pattern in Silverlight - Caliburn, MVVM Light Toolkit and GoodLight.
Should i start from own implementation of pattern or use framework?
Is this frameworks only a project solutions in which i can insert my code?
Which framework is the best for novice and which for professional?
I ask for this, cause i must start to rewrite my app from asp.net to Silverlight and i don't know that i can do it first and later (when i understand MVVM pattern and framework) implement this pattern in finished app ? Or from begining rewrite project to MVVM framework?
Going from ASP.NET to Silverlight is likely to require a (nearly) complete rewrite. The usage scenario is quite different. Silverlight is all about providing a client-side like development environment - it makes it so you can write an application the same way you'd write a client-side, desktop application, but execute this within the context of a browser.
This has fairly broad implications on how you'd use and develop your software.
That being said - for frameworks... Personally, I'd recommend getting a good grasp of MVVM first, then choose a framework (if any). MVVM is really a simple architectural design pattern. Once you understand it, the frameworks will make more sense. It's difficult to suggest "pick this framework", since they all add their own, valuable, additions and ways of working.
There are many good sources for learning about MVVM. Personally, (I'm being biased here), I like the intro I wrote (even if it's WPF oriented instead of SL oriented, the concepts are the same). That being said, Jerimiah Morrill's MVVM for Tards is also very good to get a basic understanding of what, exactly, it means when you say MVVM.
Once you understand this, the frameworks will be much more approachable (or avoidable, if you don't want them).