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.
Related
I have a WPF GUI application based on MVVM design and data binding. Now, I want to reuse the core code (i.e. the data model) in a Windows service, or a console UI app, or a WinForms app.
Is such a design reasonable? If yes, what are the pitfalls?
Or should I make a standalone data model instead, and interface WPF via wrappers?
UPDATE:
Sorry, I should have been more precise. Let me clarify: I don't doubt the very modularity thing =) My concern boils down to having my current DataModel implement INotifyPropertyChanged, use DispatcherTimers, etc. -- all that non-GUI but still WPF stuff. The model's business logic is based on it.
Is this (non-GUI WPF) design acceptable for reuse in the aforementioned cases, or should I abstract further, until no references to WPF would be required at all?
Yes, this is perfectly acceptable and most of the time it is desired!
When you build an MVVM app, it should be in at least 3 formal layers:
Presentation WPF, UI, xaml, behaviors. All that stuff. Not reusable
Application The view models and structure that supports your application rules. All that stuff. Not intended for reuse
Foundation Database access, business objects. Domain specific algorithms. Ideally this bit should be reusable anywhere
The foundation layer is the clever bit. This is where the meat in your application sandwich is. It makes perfect sense for this to be totally agnostic of UI technology. WPF, winforms, ASP. It shouldn't even need a UI.
Edit for question update:
Removing all references to WPF is hard because sometimes you need a CollectionViewSource on your view models for grouping/filtering of results. That is a WPF class.
It is very tempting to view your seperation-of-concerns as 'just dont reference wpf' and that helps but it can make life difficult. Instead, try to be disciplined with the type of behaviors you are putting in. If you find yourself writing 'clever' (domain) code on a view model, shift it to the foundation layer as a business object method or extension. Similarly, if you find yourself implementing IValueConverter often, perhaps you should make better use of view models.
One thing is for sure, your foundation layer should never, ever, ever reference WPF.
Such a design is very reasonable! You can create a portable C# library for all .NET technologies including WPF, WinRT, ASP MVC, etc which can contain your models. Obviously you'll need to wrap these portable models into a viewmodel anyway, but IPropertyChanged is implemented in all XAML flavors.
I'm used to working in WPF with the MVVM design pattern, but I've recently been asked to do something in ASP.Net. I'd like to try using MVC because I saw it referenced a lot when learning MVVM, however I don't know anything about it.
I can find plenty of sites that are meant to explain MVVM to someone who is familiar with MVC, however I cannot find a good one that explains MVC to someone who is used to MVVM. There are sites that explain MVC on it's own, but I'm having a hard time understanding them because my mind keeps trying to apply MVVM logic.
So, are there any good sites that can explain MVC in terms that someone used to MVVM can understand? Or can someone explain it to me here?
When you come from MVVM pattern and start with MVC pattern (especially ASP.NET MVC) I would suggest to think of the "MVC" pattern better as the "VMVC" because the "M" in MVC is not the Model meant by the "M" in MVVM. It actually corresponds to the ViewModel. I don't know if that represents the general definition of MVC but it is true and the most used and best practice when you work with ASP.NET MVC (although you see every now and then examples or questions here on SO where domain entities are used in a view (which is sometimes exactly the reason for the problem described in the question)).
The first thing I usually do when I create a ASP.NET MVC project from one of the Visual Studio templates is to rename the created folder "Model" into "ViewModel". If you take a look what the template code does with those "Models" you see that they are directly used for the views, that they have data annotations for input validation, for display formats and perhaps field naming on the view. These annotations are partially used directly by the HTML helpers to produce the HTML and don't represent domain or business logic. In other words: they are ViewModels for an Razor/HTML view in the same sense as you use ViewModels in MVVM for your XAML views in WPF/Silverlight/Phone7.
The domain "Model" is actually not part of the MVC pattern as it is a part in the MVVM pattern. So, the abbreviations are somewhat misleading when you compare MVVM with MVC. As a very simplified "translation table" one could say:
MVVM MVC
---- ---
M -> Domain Model not part of the pattern
V -> View (XAML) V -> View (HTML, Razor)
VM -> ViewModel M -> ViewModel
not part of the pattern C -> Controller
I'm not sure about the corresponding thing of a controller in MVVM. In MVC the controller is usually the module which translates domain objects into ViewModels and then into views (and vice versa) - schematically:
ControllerActionForGetRequest ( params )
{
objects = GetDomainObject(params) - entities, queryables or DTOs
viewModel = CreateViewModelFromDomainObjects(objects)
view = CreateViewFromViewModel(viewModel)
}
ControllerActionForPostRequest ( viewModel )
// ModelBinder makes "viewModel" from HTML input fields, etc
{
if (IsValid(viewModel))
{
data = CreateDomainObjectsOrDtosFromViewModel(viewModel)
WriteData(data) - back to data store
RedirectToActionForGetRequest
}
else
GoBackToView
}
Which part in MVVM has this responsibility? I am not sure. I have seen designs where the ViewModel holds some reference to a repository, pulls out the Model (Domain Model) to fill its own properties and writes back into the repository through ICommand handlers. That would mean that ViewModels in MVVM also have the responsibility to be a "controller" while ViewModels in MVC are much simpler: They are more or less only property bags with metadata to provide and format data for a view.
As a final note: Personally I found the MVVM pattern with WPF much more difficult to master than the MVC pattern. ASP.NET MVC is designed from the ground to support MVC pattern-friendly development and there is not need (or even not the possibilty) to leave this way. This is not the case for WPF. The original design was built with views and code-behind files in mind, not with the MVVM pattern. I found often situations where it was very difficult to bind view elements or attributes to a ViewModel and handling this in code-behing files was much easier, thereby violating MVVM principles a bit.
I would think that you won't have any problems to get into MVC when you have experience with the MVVM pattern.
Rachel, I have not run into any ASP.NET MVC sites that are geared towards the MVVM crowd, but from first hand experience I thought the ASP.NET MVC Music Store was absolutely fantastic.
I am originally a WebForms developer, and I can absolutely attest to having a certain technology in the back of your mind while learning another, forcing your logic to shift a certain way. That was especially difficult going from Webforms -> MVC. The best advice I have is to just analyze every aspect of that Music Store tutorial as a separate entity.
Good luck, and I hope that helps.
What would be the application development process for WPF applications and silverlight application?
Like how many tiers the application is divided into and how they communicate with each other. And what steps are followed during development like design , then business logic layer.
How the data base is accessed can Linq be used or data sets are better option?
I would suggest that you start out using the WPF Application Framework. Your "tiers" should be something along the lines of:
Business "Model" logic (database, LinqToSQL/EntityFramework is great with WPF)
Your "View" which is your WPF/Silverlight controls
Your "ViewModel" which binds the Logic to your View, passing change notifications anduser interactions.
I would do these steps in order. Assuming step 1 is mostly complete since it's not really unique to WPF/Silverlight, make an interesting UI but don't tie it to your model quite yet. Then study up on ViewModels. ViewModels, strictly bound and not accessed in code behind, will give you the best results.
If you're already familiar with C#/.NET, I would also strongly suggest you check out this excellent screencast showing you how to retrofit an application to following the "Model, View, ViewModel" architecture.
The process would be the same as for any other application; that is, design an architecture to suit your requirements! However, within your actual WPF/Silverlight code, you might want to look at the Model-View-Viewmodel architecture.
MVVM is a pattern that is typically used to structure the code behind a WPF UI, though it doesn't dictate how you access your data or define your business logic. The MVVM code would sit on top of your business/data code and provide an abstraction that's suitable for the UI to work with.
This question isn't really about WPF or Silverlight as they are just UIs. The architecture isn't dictated by whether you use Silverlight, WPF or something else.
For example (and not limited to this scenario), if you are using a classic n-tier architecture, you could continue to do so while using a Silverlight front end.
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Possible Duplicate:
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...
MVVM is most commonly used with WPF because it is perfectly suited for it. But what about Windows Forms? Is there an established and commonly used approach / design pattern like this for Windows Forms too? One that works explicitly well with Windows Forms? Is there a book or an article that describes this well? Maybe MVP or MVC based?
I have tried MVP and it seems to work great with windows forms too.
This book has an example of windows forms with MVP pattern (sample payroll application). The application is not that complex but will give you an idea about how to go about creating it.
Agile Principles, Patterns, and Practices in C#...
You can get the source code at
Source Code
EDIT:
There are two variations of the MVP pattern
(a) Passive view and (b) supervising controller
For complex databinding scenarios I prefer to go with the Supervising controller pattern.
In supervising controller pattern the databinding responsibility rest with the view. So,for treeview/datagrid this should be in the respective views, only view agnostic logic should moved on to the presenter.
I'll recommend having a look at the following MVP framework
MVC# - An MVP framework
Don't go by the name (it's an MVP framework).
Simple winforms MVP video
Winforms - MVP
An example of dealing with dropdown list
MVP - DropDownList
Simple treeview binding example (poor man's binding). You can add any treeview specific logic in BindTree().
Below is the code snippet.... not tested, directly keyed in from thought....
public interface IYourView
{
void BindTree(Model model);
}
public class YourView : System.Windows.Forms, IYourView
{
private Presenter presenter;
public YourView()
{
presenter = new YourPresenter(this);
}
public override OnLoad()
{
presenter.OnLoad();
}
public void BindTree(Model model)
{
// Binding logic goes here....
}
}
public class YourPresenter
{
private IYourView view;
public YourPresenter(IYourView view)
{
this.view = view;
}
public void OnLoad()
{
// Get data from service.... or whatever soruce
Model model = service.GetData(...);
view.BindTree(model);
}
}
As it has already said, i always worked in a MVP pattern when using Winforms. But the design pattern you will use not mean you will use right. There is loads of anti-pattern attached to MVP.
If you want to starts everything in a good manner, you have to use the framework for building smart client. So i will recommend to use that design and practices: Smart Client Software Factory http://www.codeplex.com/smartclient
You have a discussion here about the current smart client frameworks : http://codebetter.com/blogs/glenn.block/archive/2008/05/10/prism-cab-and-winforms-futures.aspx
PS: I like this post on the MVP anti-patterns: http://blog.mattwynne.net/2007/06/13/mvp-smells/
Hope this helps
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.
I have written about a variation of MVP/MVVM design patterns called MVP-VM, which is a tailor made solution for winforms applications that require full testing coverage and use data binding as main mechanism for keeping the presentation updated with model data.
MVVM for .NET Winforms
MVVM (Model View View Model)
introduces similar approach for
separating the presentation from the
data in an environment that empowers
data binding (WPF). Since .NET
framework 2.0 already offers advanced
data binding infrastructure that also
allows design time binding of
application objects - the ‘View Model’
entity can fit quite well in MVP based
environment.
I asked this same question to two of my techies co-workers: is MVVM for WindowsForms possible? Both gave me the exact same answer: "No way! WindowsForms is missing the rich bindings of WPF and Silverlight (OneTime, OneWay, TwoWay, OnewayToSource) and it is also missing the TypeConverters."
Screen Activator Pattern for WindowsForms - you can find it here, ported from Caliburn.Micro by jagui
Rich Bindings and TypeConverters - Truss by Kent Boogaart, does it in an UI independent way
Commands - WPF Application Framework (WAF) has a WafWinFormsAdapter project that takes care of some MVVM stuff namely commands
Again, can we have MVVM for WinForms?
Yes we can. We have all the pieces. We just have to glue them together.
I believe that MVP is a pattern well-suited to WinForms development - as is partly evidenced by it's use in CAB - Microsoft's framework for WinForms.
I use MVP in WinForms to extract code out of the View - because I can't test the View code. And also to enable code that needs to be reused (or is duplicated) to stay out of the View where it can't be shared.
I can refer to my own project where I use the MVP pattern ExceptionReporter.NET. Though I'm sure I don't use it perfectly.
You mentioned MVVM working for WPF - I think the reason for that is because of strong data-binding support. If you were not using data-binding in WPF (and it's certainly not compulsory) then you could choose MVP. The point being that MVP is a strong choice for any client-side application. And possibly a 'better' choice, even in WPF, if you plan on sharing code between projects that aren't WPF.
For more evidence of the value of using MVP in WinForms see Boodhoo's video presentation on using MVP:
http://www.bestechvideos.com/2008/06/29/dnrtv-show-14-jean-paul-boodhoo-on-model-view-presenter
And an MSDN article by the same author at http://msdn.microsoft.com/en-us/magazine/cc188690.aspx
The BindTree method seems a little
flawed to me. Suddenly the the View
knows abou the Model. Is that a good
thing? There must be tons of poeple
being confronted with these kind of
problems. I am surprised that there
aren't any books about it. Since there
are books about everything in the .NET
world.
These Design not about hiding the model rather precisely defining the interactions between the different layers of the applications. You can change the backend completely and as long as you pass a Model through Bindtree your UI will continue to work.
Now class Model may be a poor choice of a name in the example that Rajesh gives. It can be TreeData, or RecordsData. However you define it, it has what you need to using the binding mechanism of Winforms to bind a specific control to the underlying data.
The best site to browse for this kind of material is here. Martin Fowler has collected a variety of useful UI design pattern and enterprise design patterns.
Again the key to this is the use of interfaces to precisely define how each layer interact with each other.
In my own application (a CAD/CAM applications used to run metal cutting machines) my structure looks like this.
Forms implementing form interfaces
UIDLL with views implementing view
interfaces that interact with forms
through the form interface. The
specific views register themselves
with UIViewDLL Views executes Command Objects found
in command libraries that interact
with the Model.
Command libraries; lists of
commands implementing ICommand.
The command that interact with
views do so through the interfaces
exposed in UIViewDLL.
UIViewDLL; exposes the View Interfaces
used by the commands.
Model; the classes and collection that
make up core data structures of my
application. For me these are things
like material, cuttingpaths, shape,
sheets, torches, etc.
Utility; a DLL that has commonly used
utility classes used by my company
that span different application. For
example complex math functions.
You can use Enterprise Architecture, Patterns and Practices as the starting point, although they are slightly dated.
Under General Guidance there is Application Architecture for .NET: Designing Applications and Services, which is a good introduction to .NET ways and layered N-tier application.
alt text http://i.msdn.microsoft.com/ms954595.f00aa01%28en-us%2CMSDN.10%29.gif
For more formal "patterns", there is Enterprise Solution Patterns Using Microsoft .NET.
(source: microsoft.com)
To name a few,
Model-View-Controller
Intercepting Filter
Three-Layered Services Application
The first good explanation of UI design patterns I read was in Jeremy Miller's blog - Building Your Own CAB. It describes the common patterns - Passive View, MVP, etc. and addresses some of the ways you might implement them in C#.
You can try MugenMvvmToolkit that allows to use a "pure MVVM" for WinForms.
Due to the fact that it supports bindings on all platforms, all of the native binding features available for WPF platform available on all platforms (include WinForms).