By default ActivityDesigner set its DataContext to "this" (the ActivityDesigner itself). The ModelItem type and is available through the ModelItem property and represents the Activity you are doing a designer for.
Would it be a good idea to use MVVM for ActivityDesigner ? I don't think so but I couldn't find any article on it.
Your Activity is your ViewModel. And the ModelItem is where you mix in what does not exist within the Activity.
The ModelItem wraps your ViewModel to provide for all the UI facilities that do not need to exist within the Activity itself, such as undo/redo and change notification.
It also, and possibly more importantly, provides for attached properties which you can use to mix into your Activity ViewModel-ish facilities that do not and should not exist within your Activity.
Related
I am loading controls dynamically from the web server from separate XAP files. After creating an instance I want to show them in tab Pages. The controls can be MMVM controls using CM but also non MVVM standard controls.
Before trying the tab I tested to simply show a control dynamically on the page by using:
<ContentControl Name="TestControl" />
Test control is a property of Type UserControl which is set via creating a new Instance of a dynamically loaded control. Now this gives me an error that it can't find the view. In case of non MVVM controls there is of course no view, so how do I load a non MVVM control?
I tried to make the test control a MVVM control, but still get the cannot load view error. Makes sense as such instance is not created. If I create an instance of the dynamically loaded view besides the view model, how do I "Add" this so that CM finds it?
Last but not least, how do I bind this to a tab control in Silverlight? The idea is to have a collection of user controls (plugins) which each is rendered in its separate tab page.
Thanks for any help.
(I got this done in no time NOT using MVVM, still not sure if MVVM is worth all the complexity)
There's no such thing as "mvvm control". MVVM is just a pattern not a control type. Basically, in Caliburn you don't need to work vith UserControls or Views directly, but if you pick the ViewModel first approach, Caliburn framework should be able to find the matching view for you. In your case since you're loading XAP files dynamically, you need to add them to the list of assemblies Caliburn looks to find a View/ViewModel (and bind them together) and this is done through IAssemblySource interface. According to the documentation here:
So, what is AssemblySoure.Instance? This is the place that
Caliburn.Micro looks for Views. You can add assemblies to this at any
time during your application to make them available to the framework,
but there is also a special place to do it in the Bootstrapper.
I have been using the MVVM Light Toolkit to help learn the MVVM pattern. However, I have not been able to solve the problem of usercontrols within controls scenario.
For example, in a Timesheet application, lets say we have a control called NewUnitOfWork. When it first loads, a panel with a ListBox with a list of projects is loaded as the Content of the NewUnitOfWork. The user clicks on one. A new panel is swapped in with a ListBox containing the possible tasks for that project. A task is selected and a new panel is loaded which will contain controls to input data for the chosen task of the chosen project.
So, we have the selected item in one usercontrol being passed to the other two user controls, which are, in turn swapped in as the Content of the NewUnitOfWork control (or window).
If each control has its own ViewModel, we need to pass the selected value from one ViewModel to the next etc.
I have got it working in a single user situation using global variables (via a "service"). However, there are concurrency issues with that and it is not a good solution. It's sub-par.
I have seen many times the suggestion on this forum to have on ViewModel as a member of another ViewModel. Whilst this solves the problem at hand, I believe it is a violation of the MVVM pattern. Another ViewModel is not UI-related functionality that the ViewModel shoule be directly.
So. Has anyone found a clean MVVM-complying way to do this sort of thing?
Cheers
Please always keep in mind that MVVM is just a pattern and it is designed to help you separate your UI and logic. Do not be afraid to “violate the pattern” if it helps to increase testability or maintainability of the application.
Having a master ViewModel with several child ViewModels is very handy if you have a complex UI. The main ViewModel may be responsible for handling the top level UI controls and for coordination of the child VMs, while other ViewModels are responsible for communication with the sub regions of your UI.
Moreover, if you have a really complex UI with the multiple nesting UI layers, you can implement an infrastructure to automatically cascade all the events from master to child VMs.
And of cause, you may try to use one of the more advanced MVVM frameworks. For example Catel implements pretty comprehensive model to resolve such situations with nested VMs.
I don't see a problem with ViewModels referencing other ViewModels (based on my experience with TreeViews). Have a look at any article about TreeView and MVVM. You will see that each node is a ViewModel, that references a collection of child nodes, which are ViewModels. Trying to do that without VM-VM references would be a nightmare.
Josh Smith
http://www.codeproject.com/KB/WPF/TreeViewWithViewModel.aspx
I have been using the following setup:
A 'master' VM with a 'collection' VM and a 'details' VM as nested properties.
The master VM is tied to a View that is used as a master-detail form. This master-detail View is composed from two other Views.
I find it a very neat setup because it allows me to put search criteria in the master View(Model) and keeps the other View(Model)s clean.
I can't see how this would break the pattern.
I am doing a silverlight using the MVVM model, and i am finding it hard to do the events handling via MVVM especially that the events handlers are doing lots of changes in the view like enabling and disabling buttons, update media element functions and position. I am still new to the MVVM and i can't Imagen how can i do this. does anyone already know good article to start with or simple approach to understand :) I'll reply with what i may find interesting while i do my search as well. Thanks
1) Understand that there are different "flavors" of MVVM. Strict/hardcore MVVM patterns, although theoretically desires, isn't necessary.
2) Many view events can be handled via Commands. WPF supports this, and i believe Silverlight 4 does as well. A simple view-event to start with would be Button clicks. This allows you to handle the event in the ViewModel (instead of the View's 'code-behind').
3) For things like enabling/disabling view controls/states via the MVVM model, here is an example/explanation:
Xaml controls (say, a Button) is Data-Bound to the ViewModel for whatever property
(in this case, it will be the button's IsEnabled property).
Your ViewModel has an IsButtonEnabled property.
Whenever you change this property in the VM, raise the PropertyChanged notification, and you will see the binded result in the view (the button's IsEnabled state will be updated).
ps - you can do many things via VM properties in this manner: from text, to various property states, color, you can even play animations in the property setters/getters....etc.
Cheers
I have a WPF user control ...which is in MVVM. The user control(which contains a listview) need data from the page (where it is included). I have to set a property in View's code behind to get this data input. Will this comply with MVVM(But MVVM pattern do not support adding code in code behind file of view as far as i know).if not, what is the way for the same?
You want to do this via data binding. The controls are bound to properties in your viewmodel which receives the data, applies the needed logic and gives it back to the view for displaying it.
Have a look here to get an idea on how all that works.
I have got a link : http://social.msdn.microsoft.com/Forums/en/wpf/thread/a3eedc3e-0d59-420c-aba0-44fe8b00552f
But I'm not really getting whats meant by injection in it (as given below) :
an interface to the UserControl public model called IUserControlModel. It has the properties that should be visible from outside;
- a UserControlViewModel that contains a public property of type IUserControlModel that is injected in the constructor; plus all the properties used for XAML binds specific to the usercontrol implementation; XAML may have binds directly to the IUserControlModel properties too;
- a MainWindowViewModel that nests the IUserControlModel inside.
I think your problem can be solved in easier way. If you expose ItemsSource property of ListView as Dependency Property of your user control you can achieve what you want without unnecesary (in this case) overhead of implementing MVVM pattern : You then can just use databinding to add data from the page where the user control is included.
post that I think answers your question :
Post link
I have a plugin which contains class A that brings up a view defined in class B via the following line of code:
(VideoLogView) PlatformUI.getWorkbench().getActiveWorkbenchWindow().getActivePage().showView("Videolog.VideoLogView");
What I need to do in the createPartControl() method of the view (class B object) is access a method in the class A object.
How can this be done?
Thanks.
Look like you are facing the classic issue of "how do I pass arguments to my view" ?
This thread illustrates it best:
I was facing the same problem at the beggining of my RCP project. I was getting weird about the fact that there was no way to pass an argument to a view as the viewed model.
Why? Because (emphasis mine):
You are on an opened, pluggable platform.
You contribute to existing developments, others should be able to contribute to yours.
Therefore you will not "pass" arguments to a view, this would lock the whole thing into a non-opened design.
Instead, your view will ask the platform (or will listen to the platform) to determine which information to manage.
Other views (from other plugins that don't yet exist) might also want to manage the same information on the same event.
What you should do then is to ask the workbench for the current selection. I guess your view is opening on a double click action or simple selection so the object you want to manage in your view will be currently selected.
This is how you could retrieve the workbench selection from your view :
ISelection s = this.getSite().getWorkbenchWindow().getSelectionService().getSelection();
where "this" is a ViewPart.
Then you have to make your initial view (the one initiating the view creation from a given event like DoubleClick) a selection provider. A JFace viewer is a selection provider, so you can use it if you're using jface, or you can implement the ISelectionProvider interface when you're using custom SWT controls (that was my case).
The article "Eclipse Workbench: Using the Selection Service" can also give you some pointers.