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.
Related
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 currently working on a brownfield application, it's written with winforms,
as a preparation to use WPF in a later version, out team plans to at least use the
MVVM/Presentation model, and bind it against winforms...
I've explored the subject, including the posts in this site (which i love very much),
when boiled down, the main advantage of wpf are :
binding controls to properties in xaml.
binding commands to command objects in the viewmodel.
the first feature is easy to implement (in code), or with a generic control binder, which binds all the controls in the form.
the second feature is a little harder to implement, but if you inherit from all your controls and add a command property (which is triggered by an internal event such as click), which is binded to a command instance in the ViewModel.
The challenges I'm currently aware of are :
implementing a commandmanager, (which will trigger the CanInvoke method of the commands as necessery.
winforms only supports one level of databinding : datasource, datamember, wpf is much more flexible.
am i missing any other major features that winforms lacks in comparison with wpf, when attempting to implement this design pattern?
i sure many of you will recommend some sort of MVP pattern, but MVVM/Presentation model is the way to go for me, because I'll want future WPF support.
Thanks in advance,
Erik.
Please take a look at Update Controls .NET. It is an open-source library for Winforms, WPF, and Silverlight that keeps controls up to date as data changes. You can start using it now for Winforms, and then transition over to WPF without changing your Data Model or View Model code.
Unfortunately, it does not solve the Winforms command binding problem. Your button click events will not port from Winforms to WPF. But it does take care of the data binding problem.
You might find the WAF Windows Forms Adapter interesting. It shows how to apply the Model-View-ViewModel (MVVM) Pattern in a Windows Forms application. The Adapter implementation provides a solution for the missing Command support in Windows Forms.
I am thinking about the design of a WPF or Silverlight application. I am planning to use MVC (or another such design pattern)
Witch ever of the design patterns I choose, I need to connect to view to the model (or presenter) – is databinding a good way of doing this?
(In the past with WinForms applications I have found that Databinding give lots of problem in the long run and does not fulfil its promise. It is the same with WPF and Siverlight?)
Yes, you should definitely definitely use data binding. While WinForms and ASP.NET were always a struggle to get anything data bound consistently and in a maintainable manner, Silverlight and WPF are built from the ground up for data binding pleasure.
Binding is two-way so you don't have to write tedious plumbing code to move data in and out of your model. Just implement INotifable and away you go.
Converters allow you to write code to handle the way things are bound if the defaults aren't working. Using converters (which are dead-simple to write) you can bind booleans to visibility settings, strings to images, integers to background colors, and so on. The sky's the limit.
Patterns such as MVVM are perfect for the rich data-binding support in WPF and Silverlight. MVVM lets you have the best of both worlds: loosely coupled code together with data binding.
Element binding lets you bind the property one element to the property of another element. Together with converters, this gives you impressive power to do things like bind the current position of a slider control to the selected index of a list control. Both ways.
Deep binding means you can bind to the property of a property of your model. Not that you always should, but you can.
Binding is almost magical in its dynamic-ness. As long as your model continues to support the same bound properties, binding will continue to work even if the static type of the model changes. Binding is also crazy flexible. You can bind to collections, interfaces, complex objects, (almost) anything you like.
DataContexts can be used to set up data-binding at a page, control, or container level. Children of the container then inherit the same data-context. This lets you bind once at the page level and then use binding paths for the rest of the page.
I recommend you take a look at the Model-View ViewModel (MVVM) pattern. Here is a very good video you should take a look at: Jason Dolinger on Model-View-ViewModel. Two-way data binding in WPF is very powerful.
be it WPF or Adobe Flex or Winforms , Databinding will always give issues when the application becomes complex. I would prefer to avoid data binding for easier debugging. But data binding runs all around WPF that we can't avoid. Doing data binding in XAML takes away control from the developer.
I think , if we keep the data binding in the code , its much easier to debug.
Imagine , MVVM without data binding , it will look messy. A design pattern that takes advantage of technology is good but a design that is totally dependent on a particular feature is a disaster.
Data binding in WPF goes far beyond what you could achieve in Winforms. It is intrinsic to the platform and prevalent throughout. I would argue you can't understand WPF without understanding its data binding system.
It's not without its pitfalls, to be sure. Broken bindings are often not as obvious as you may like, but improvements have been made to help you identify and flag these issues.
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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...
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/