I'm writing an application in wpf that uses MVVM. I wondered if I could use ado.net entity data model as a model in MVVM? Is it the same? If not, why?
Thanks for any help.
Regards,
Ev.
Sure, you can use the Entity Data Model as Model part of the MVVM Pattern.
You might have a look at the BookLibrary sample application of the WPF Application Framework (WAF).
This MVVM sample application uses Entity Framework data models as well and it is composed of various Views (UserControls).
as I understand, one can use the entity model. but you will finally have tied coupling with the entity framework. whenever you plan to exchange your model for eg. with another ORM, you'll have more work to replace the model.
better is to use a repository pattern for data access. with this pattern you have more flexibility in the end. similar question here
Related
I created database in management studio, a model in my project with the ADO.NET Entity Data model for the tables.
I want to use the MVVM pattern to build forms and update, delete, insert data in my forms.
Can you please give me some guidance how to map the models with my viewmodels. Any tutorials would be nice, I`ve already spend whole day looking for something but got confused at the end.
Is there a simple project with Entity Framework and MVVM.
This is a bit of a contentious subject but I personally don't view change notification as belonging in the exclusive domain of the view/view-model relationship, so I add INPC to my models as as well and expose them in their corresponding view model. This can be done by either injecting proxies into your repositories at runtime (e.g. Castle Dynamic Proxy) or by modifying the IL automatically at compile time (e.g. Fody).
From one noob to another - try searching for 'wpf mvvm entity framework example'. Here's what I found useful...
http://www.software-architects.com/devblog/2010/09/10/MVVM-Tutorial-from-Start-to-Finishhttp://social.technet.microsoft.com/wiki/contents/articles/28209.wpf-entity-framework-mvvm-walk-through-1.aspx
First you can use the repository pattern, to abstract your data access layer, so you viewmodels don't have a tight coupling to Entity Framework and remain easy to test.
Second, you can use an auto mapper like AutoMapper to map from your models to your ViewModels. However, you shouldn't use automappers to map from ViewModels to the View, so you'll have to manually create your model and pass it to your repository for insertion or updating.
I'm creating a WPF application with MVVM framework. The data is then retrieved by accessing a WCF service exposing the data based on Entity framework model. Is there anything wrong with this? It seems that the "Model" portion of MVVM seems to be missing.
There is no issue with the design. Ef wcf part will act as model.
Silverlight-Application-with-MVVM-WCF-and-EF
Silverlight-with-MVVM-and-WCF
I am trying to create a WPF project with MVVM and ADO.Net Entity Framework.
I do have a few questions though.
Do i create the Entity Framework Model in the Model Folder of the MVVM Design?
Or do i have to create a new project for each item of the MVVM Model(i.e Views Project as
a WPF Project,Model Project as a class libraray, ViewModel project as a class library)?
It doesn't really matter where you put stuff, but yes I usually put all my EF or Linq-Sql stuff in a Model folder as they will usually house all of my model classes anyway and it keeps it all together. It is a bit of a grey area though, because it's also doing DataLayer stuff, so just bear that in mind too.
Regarding your 2nd point, no. The Model, View Models and Views should all be in the same project.
Take a look at this for some guidance on MVVM.
Do i create the Entity Framework Model in the Model Folder of the MVVM Design?
I usually create a separate project for the model which is storage ignorant (using POCOs) and also usage ignorant.
Or do i have to create a new project for each item of the MVVM Model(i.e Views Project as a WPF Project,Model Project as a class libraray, ViewModel project as a class library)?
If you are planning on having more than one type of view-model per model (e.g. one for WPF, one for a service, one for another service), then separate your view-models into their own assembly.
If your views only represent one model layer, then you can start out your views and view-models in the same assembly, then separate them if you get to a situation that you have multiple models under the same view (each with its own view-model).
You should also consider if you want the ADO.NET's model to be your main model (upon which you base your view-models), or if you want to treat it as a sort of view-model for storing (where the storage service is a sort of view).
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.
[Disclaimer: I'm ASP.NET MVC Developer]
Hi,
I'm looking for some best practices with implementing MVVM pattern with WCF RIA in Silverlight 4.
I'm not looking to use MEF of IoC for locating my ViewModels. What I would like to know is how to apply MVVM pattern with Silverlight 4 and WCF RIA.
I don't want to use other stuff like Prism or MVVM Light toolkit. I found many examples on Internet showing how it is wonderful to drag and drop a datasource on the view and the job is done (it reminds me about my first VB6 developments).
I tried to implement MVVM with WCF RIA and it's not strightforward at all. If I understand, the MVVM should contain all the logic in order to unit test it in isolation but when it comes to combine it with WCF RIA it's another story. I have the following questions.
Can I use a generated metadata as model ? It would be easier to use it that if I write all from the scratch.
As I saw the only way I could get data is through DomainContext or through direct binding in the view (local ressource). I don't want the direct binding in the view, not testable at all. On the other hand I can't use DomainContext, it doesn't expose any single entity !!! All I have is the EntitySet that I can bind to datagrid. How do I bind a single Entity to the DataForm from the ViewModel ?
How do I udpate the model to the database ?
How do I navigate from one Entity to a collection of it's items. For example if I have a Company Entity I would like to show a DataForm to update an entity informations and a datagrid to show companies adresses. When saving a form, I would like to save an information to Company and an information to adress about which adress was selected as active.
Please help me understand how to do it well. Or maybe I should drop the WCF RIA and to do it with WCF from scratch ?
What do you think ?
You might be interested in this session. It explains how to use the MVVM pattern with RIA WCF Services.
I found this post useful:
http://www.astaticstate.com/2010/04/silverlight-4-using-mvvm-patter-ria.html
Some random answers...
I don't think that MEF is particuarly well suited for Silverlight. It's primarily for desktop apps, and could be adapted for other uses where the plug-ins are in the local file system relative to the app.
MVVM requires that you understand roles. The "view" is your XAML and code-behind. The code-behind should handle events from the user control, but very little more than that.
The ViewModel holds the data that the user control will bind to. Generally, the ViewModel is bound to the View as its DataContext, so that everything in the form can databind to properties in the ViewModel. The ViewModel must implement INotifyPropertyChanged, and raise property changed events for every property that the form databinds to.
You'll probably want to create an ObservableCollection, using an EntitySet as your source. This will handle INotifyCollectionChanged for databinding purposes. If the entities in the EntitySet also handle INotifyPropertyChanged, then you're in good shape on databinding for collections.
You can create a property for an individual entity, and databind to that, assuming that change notification is also implemented (both for entity members, and for the entity property).
RIA Services will regenerate the DomainContext on each build, which helps a little in keeping it in sync. It's intended to be a service layer above an ORM, though, so your ORM or other data mapping will still have to be maintained by other means.
I haven't looked at the final release of RIA Services, but I wasn't hugely impressed with the beta version. I'd rather have good entity classes defined on the server, and share them with the Silverlight project. It's not easy to set up, though, and requires some non-trivial WCF that doesn't rely on service referernces. (RIA Services final release may have cleaned some of this up, but the native WCF service reference in Silverlight is pretty much evil, mainly because it doesn't automatically recreate generated classes, and it hard-codes the URI for the server-side service.)
Metadata was another problem with RIA Services beta. It's easier to attach metadata attributes directly to your DataContract class and the individual DataMember properties, if you control the entity source. Again, that may mean not using RIA Services. Writing a separate metadata class, as was required for the RIA beta, wasn't a good solution.
I ended up not using RIA Services for Silverlight 3, and didn't regret it. Here's an excellent article on WCF and Silverlight. Although it says Silverlight 2, it's still on-target for any Silverlight release.
I do recommend MVVM Light. Source is available on Codeplex, if that's an issue. It provides messaging and commanding support, as well as a ViewModelLocator; while the latter takes a bit of work to understand, it's really a good extension to the basic MVVM model.
Hope this helps.....
Just thought I would let you know about a project I am working on - just got our first release done. Provides a great simple way to approach MVVM for Silverlight + RIA Services specifically. Simplifies a lot of the MVVM stuff, and provides some more controller-like functions with the Notifications class. http://slmvvms.codeplex.com/