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UI Design Pattern for Windows Forms (like MVVM for WPF)
Should MVVM be used for WinForms? If so, what is the advantage over using MVP?
I think that there are two answers here... really just one answer to "Should I" and one answer to "Could I".
As far as "Could I", it is certainly possible. MVVM really just relies on a view that can bind to a view model. Since WinForms supports binding, this certainly is possible. You may need to write some code to make that binding more useful in an MVVM world, but it is (at least) theoretically possible. If it worked well, the benefits would be pretty great, IMO. You could make sure that your WinForms "View" had no UI behavior, except for creating the visual objects and binding them (in code, not declarative like in XAML). WinForms objects are very difficult to test, where ViewModels are very easy to test.
As far as your real question: "Should I", that becomes much more of a project-level decision. What are your goals? If you are looking to make some rather complex UI logic testable, then you might at least look into it. Fortunately, though, there are other patterns (Model-View-Presenter, for instance) that have more community backing that also has you write a testable "presenter" class. I find ViewModels significantly easier to write unit tests against compared to Presenters, but I think that is a personal preference.
Just as an aside, the MVVM pattern is mostly another name for the "Presenter Model" pattern. You might look to see if anyone is having success with the "Presenter Model" against WinForms UIs.
Good luck!
The Model-View-ViewModel (MVVM) Pattern is a design pattern. Per definition a design pattern shows a common solution in the object-oriented world and this solution can be applied in various platforms (WPF, WinForms, Java Swing, etc.). I agree that MVVM is best used with WPF because it leverages the strong binding capabilities. However, Windows Forms supports data binding as well.
The WAF Windows Forms Adapter shows how to apply the MVVM Pattern in a Windows Forms application.
MVVM Specifically fits the markup + code and lookless model in WPF and silverlight. I would not suggest it to a winforms app as I believe it would be an overkill. I do not see any benefit over MVP in a winforms app. However in WPF and silverlight it is always the preferred than MVP.
Read up on the web what MVVM is and why it came to be. That should clear it up further.
I don't believe MVVM can be done in winforms(at least not without a lot of hacking). MVVM separates the view(your form) from the viewmodel(your logic).
The reason it can be done in WPF is because WPF allows loosely coupling the view from the viewmodel via databinding in xaml. This allows the ViewModel from not knowing anything about the view and still being able to function. This is a good article on MVVM basics, I believe that it will clear up several questions.
MVVM was specifically created for WPF, in order to take advantage of WPF features like bindings and commands. Windows Forms doesn't have these features(*), so it doesn't really make sense to try to apply the MVVM pattern to a Windows Forms application... You should probably use MVC or MVP instead.
(*) It actually has some basic support for data binding, but not as powerful as in WPF...
Related
I'm familiar with WPF technology, specifically MVVM methodology. Recently I began to program in Winforms, and I was wondering- Does using data-binding in winforms (combined with INotiify...) is considered the best practice, or is it an overkill?
Some people say that data-binding is a real pain in the ass in winforms, is that right?
And just to make it clear: I'm not talking about full MVVM implementation in winforms- simply binding data to controls (text boxes and such, not buttons).
Data binding in Windows Forms works very differently than WPF - and is (IMO) a bit more of a pain. The main issues are there are more restrictions on the binding source, and there isn't a clean way to handle things like IValueConverter, so there is typically a lot of extra work involved in getting anything but very simply binding to work cleanly.
Details on how to use data binding in Windows Forms are described on MSDN in Windows Forms Data Binding.
In MVC a model can have multiple views, in WPF a XAML code-behind model is tight to 1 single XAML (view) isn't WPF/XAML flawed from the start in respect to MVC ?
I recommend looking at MVVM for use with WPF.
You're comparing MVC with Windows Forms to WPF with code behind - which is comparing an architectural pattern to a technology (without using a pattern). This is an unfair comparison.
I wrote a series on MVVM starting from a Windows Forms perspective that may help with understanding this. You'll find that the separation of View and ViewModel possible with WPF is far cleaner and simpler to implement than the Controller of MVC. It actually allows even more decoupled architectures with less implementation work.
Good question!
In MVC you state that a model can have multiple views, which is true. However, each view would have its own controller.
In MVVM a model can have multiple views, and in this case each may have their own view model.
However, in practical terms, if a ViewModel does not have any concepts that are highly specific to a certain view, it is entirely possible to re-use view models. In fact, I wrote an article on cross-platform XAML applications where I re-used code between three apps, one on WP7, one in Silverlight, the other WPF:
http://blogs.msdn.com/b/mikeormond/archive/2010/12/09/writing-cross-platform-xaml-applications.aspx
The views for each were very different, however I was able to re-use both the models AND the view models for all three apps.
WPF/XAML is a technology, and MVC is design pattern, it's good when technology is not limiting you to a specific pattern, and allows developer to choose what pattern to use. Same as programing languages allow's you to use any design pattern.
You can use MVC, MVP, MVVM, or YourMegaPattern with XAML\WPF. Technology should be above patterns, it's frameworks that are usually bound to a specific pattern.
For example you can take ASP .NET techology, and MVC framework based on it.
Does the code behind file have the same purpose as a Control class of MVC or the Boundary-Control-Entity Pattern?
I did some small projects with Silverlight and WPF, and most of the time I pretty much put the logic in the code behind file. Though with references to other classes. Not everything in the code behind.
What was/is the initial purpose of the code behind file and how do most of you use it?
Thanks,
Grant
The preferred design pattern for developing Silverlight applications is MVVM, in which the View Model is closer to taking over the role of a controller in MVC. When using the MVVM pattern, I'd only use the code behind of controls to implement UI-only (view-only) logic that has little to do with the data, such as performing animations and other special effects.
Originally, the code-behind file, in conjunction with data converters in WPF, served the same purpose as the code-behind in VB6, C#, VB.NET, what have you. It is primarily a place to put code that responds to UI events. However, in the case of WPF and Silverlight, coding in the code-behind file is potentially very messy and can easily lead to maintenance problems later on, if there is anything more than the simplest program to be implemented.
"Model-View-ViewModel" (MVVM) was conceived, I think, late in the development of WPF; Silverlight was conceived later than MVVM. Near as I can tell. Not every consultant I've heard talking about WPF or Silverlight is convinced that MVVM is "the preferred" design pattern, but it is a solid abstraction model.
WPF isn't as well tooled as WinForms, even today. This is part of what makes it potentially very messy with the potential maintenance problems. MVVM, as a design pattern, makes up for a lot of the drawbacks stemming from the immaturity of XAML and WPF/Silverlight as a user interface model, while bringing forward most of the tremendous advantages offered by XAML and WPF.
Summaries of MVVM are available here, here, and here. Josh Smith is a leading authority on the pattern, he sells a book called "Advanced MVVM" which I'm told is useful; I was able to implement some complex implementations without it, though.
I'm a newbie to WPF and I'm developing a brand new windows desktop application and I would like your opinion on what WPF framework I should use. I know this question has been asked before, but the last question was asked at least several months ago. A lot has changed since then.
Right now, I'm using MVVM Light which is more of a library than an actual framework, as the name suggests. I’m looking for something more comprehensive. I prefer a framework that I can use on future WPF projects. Consequently, it should be general purpose and productive.
Any insights or suggestions?
If you are a newby I would suggest that you try to use PLAIN WPF first to get a feeling for it instead of right away extending WPF with other frameworks.
Your title is a bit confusing. WPF is just a graphics/UI layer. WVVM is a Model View ViewModel framework, for implementing a MVVM pattern using WPF ( or Silverlight ).
So, are you asking what design pattern you should use for your WPF application? ( As in MVC, MVVW, MVP, etc... ) Or are you asking which MVVM frameworks are compatible with WPF?
Ugh, acronym soup.
As to my answer, if you are new to WPF and want to learn WPF, I would start with no framework, you can always refactor later once you have a good solid grasp of the underlying technology.
It's definitely on the heavy weight end, and plenty of people will warn you about it, but you seem to be asking for CAG
http://compositewpf.codeplex.com/
It's a pattern that comes with a sample implementation that you can bend into your own. For example, it comes with Unity for IoC, but you should be able to put in another IoC container.
The download comes with a lot of samples for both Silverlight and WPF.
Caliburn (http://caliburn.codeplex.com/) handles a lot of shortcomings of the WPF inherent model (like writing a ton ot stupid routing code for events) and introduces MVVM ;) My bet ;)
You might have a look at the WPF Application Framework (WAF). The sample applications show:
View composition
UI Workflow (Wizards)
Command binding / Shortcut Keys
MVVM pattern, Unit Testing
Validation
Entity Framework
Open/Save FileDialog
Print Preview / Print Dialog
Localization
One challenge with Silverlight controls is that when properties are bound to code, they're no longer really editable in Blend. For example, if you've got a ListView that's populated from a data feed, there are no elements visible when you edit the control in Blend.
I've heard that the MVVM pattern, originated by the WPF development community, can also help with keeping Silverlight controls "blendable". I'm still wrapping my head around it, but here are some explanations:
http://www.nikhilk.net/Silverlight-ViewModel-Pattern.aspx
http://mark-dot-net.blogspot.com/2008/11/model-view-view-model-mvvm-in.html
http://www.ryankeeter.com/silverlight/silverlight-mvvm-pt-1-hello-world-style/
http://jonas.follesoe.no/YouCardRevisitedImplementingTheViewModelPattern.aspx
One potential downside is that the pattern requires additional classes, although not necessarily more code (as shown by the second link above). Thoughts?
I definitely think you should use the MVVM pattern for Silverlight applications - and one of the benefits of the pattern is that you can actually make your application really blendable through some simple techniques. I often refer to "blendability" as "design for designability" - that you use certain techniques to make sure your application looks great in Blend.
One of the techniques - like Torbjørn points out - is to use a dependency injection framework and supply different implementations of your external services depending on wether the code is being executed in Blend or in the Browser. So I configure my container to use a dummy data provider when the code is executing in Blend, and that way you get design time support for your list boxes, data grids etc.
The challenge is often how to set the DataContext declaratively - so I often end up using a service locator class a a "front end" to the IoC container. That way I can bind the data context to a property on the service locator.
Another technique is create some kind of ObjectDataSource control (non visual) that has two properties: Design Time DataContext and RunTime Data Context. The control does the job of detecting where is being executing, and then setting the Parent DataContext to the right object.
I'm not sure if I can answer your question, but I have foudn the article below very valuable. Jonas Follesø is using ninject to switch out his services when in design/blend mode. Very nice!
http://jonas.follesoe.no/YouCardRevisitedImplementingDependencyInjectionInSilverlight.aspx
I also agree with Jonas regarding MVVM with Silverlight. I do believe that MVP is also a good choice, but recently I have had time to try both MVP and MVVM with Silverlight and I am much happier with the results from MVVM. (Yep, I changed my mind the more I used MVVM). The VM abstracts the binding of the Model from the View (obviously) in MVVM which allows for more binding scenarios (at least cleaner ways to do them) than with MVP. That's just one aspect, though.
I'll be posting some examples of both MVP and MVVM with Silverlight on my site.
I've tried a few options and I'm settling on MVVM as the best choice for me. Blendability is an important point, and I also find the VM aspect intuitive for rigging up dynamic behaviors and procedural effects and animations (like Nikhil's Silverlight.FX). At one point I tried to avoid Blend altogether through fluent interfaces but am finding the coupling between UI and behavior too painful in the long-run. I want to design my UI in Blend and then add effects and other behaviors in code, this is proving to be the best pattern for me to follow so far.
I think many of us are waiting for the trailblazers to go ahead and create really good sample apps using MVVM in Silverlight (and WPF for that matter). There are a number of tricky areas such as the lack of ICommand in Silverlight, or the difficulty of interacting with animations starting and stopping only using data binding.
Its definitely a pattern to watch for the future though, and is worth trying out if you don't mind 'cheating' occasionally in the places where you can't quite figure it out.
I love the ViewModel pattern and highly recommend it. I have a couple of "getting started with ViewModel" types of posts on my blog.
ViewModel Pattern
HelloWorld.ViewModel
Binding Converts - VisibilityConverter
Silverlight Airlines with a ViewModel
I agree with Jonas. MVVM seems to be the model that works best for me (though John Papa thinks MVP makes more sense). I have an MSDN Article on this coming out in March that hopefully will answer the call for a good example.
BTW, I would like to see some cohesion in the MVVM Framework department. There isn't a good solution for a framework to follow yet. I like Jonas' (I think Jonas' is the FX Framework) but since its not WPF compatible it might not be the right choice for some.
I've been using MVVM lately on a couple of different Silverlight projects and it's been working really well, I would definitely recommend it. Jonas's post is a great place to start, I've recently blogged on my MVVM experiences too and created a really simple solution to demo the main touch points.
There's a very good Techdays 2010 video introduction to the MVVM pattern, clearly explained:
TechDays 2010: Understanding the Model-View-ViewModel pattern
Hanselminutes podcast by Laurent
For more complicated applications that require a higher degree of automated testing it definitely makes sense, and the move away from DependencyProperties to DataContext binding is a lot neater than it's ASP.NET counterpart.
The biggest challenge I've found with Silverlight is testing the actual UI (there's one commercial framework so far I think), and the huge tangle of event calls you get into when using WCF services (or the WebClient for that matter) with Silverlight.
I've always thought MVVM and PresntationModel http://martinfowler.com/eaaDev/PresentationModel.html are essentially the same thing. PresentationModel is a lot easier to say.
I've used it succesfully in java swing, windows forms, WPF and silverlight. If you think in terms of separation of concerns a Presentation Model makes a lot of sense. You have one class whose only concern is providing a Presentation friendly Model.It really doesn't matter what technology is used to show it on the screen. It might change some implementation details but splitting the concerns apart is a good idea no matter how you show the information.
Because of that separation you can easily write tests against your presentation model regardless of the view technology. So that's a plus.
With the Feb 2009 release of Prism v2 by P&P, even better support for MVVM now available for Silverlight and WPF. See microsoft.com/compositewpf for more details.
Take a look at my article about MVVM and Silverlight in real life projects and decide for yourself.
http://alexburtsev.wordpress.com/2011/03/05/mvvm-pattern-in-silverlight-and-wpf/