I'm working on a project that utilizes WPF, using the Prism library and Unity Container.
I have a mainwindow, which contains a mainviewmodel control which in turn is populated by a collection of user controls.
My goal is to set keyboard focus to the mainviewmodel where I have an EventTrigger InvokeCommandAction which reacts to keyeventsargs...
Currently the only way the command is fired if I use a textbox within the control (or child controls). My goal is to have the mainviewmodel control or grid get and preserve keyboard focus.
Any tips would be appreciated!
//Nathan
Either not understanding your question correctly or you should review the basic concepts of MVVM in a WPF implementation.
The View is the WPF controls.
WPF Window/UserControl files contain WPF markup which is the View.
Controls in a view leverage DataBindings to the DataContext property of either the control itself or the parent containing control (which it will inherit).
DataContext property is set to an instance of an object that is the ViewModel. It contains properties to hold values and commands to execute actions.
So conceptually there is no "mainviewmodel control", there is a MainView which contains controls and may in this case have its DataContext property set to an instance o MainViewModel. (hence my confusion)
Finally, while it is possible and some might even recommend writing UI rules/logic in a view model I haven't found much benefit in it.
You are much better off putting UI logic in the XAML or in the MinView code behind. You can still access the MainViewModel in the code behind by casting the MainView.DataContext property as a MainViewModel.
So for example:
MainView.KeyDown event can be wired up to call MainViewModel.CommandX.Execute();
Related
I am trying to achieve something very similar to this:
WPF with Helix toolkit, animate with code-behind?
However, my scenarios is slightly different. I am trying to animate a tube (curve) defined by a path (TubePath) which undergoes deformation as a function of time (animation) defined by a mathematical function (calculated numerically).
My design/plan is to use a usercontrol (containing the Helix Tube control) to draw each frame of the tube defined by a path. I plan to make the TubePath property in my usercontrol which is an oservablecollection a dependency property. I plan to control the animation from my ViewModel (or View) by binding the CurrentPath property of the ViewModel to the usercobtrol TubePath property. I plan to drive my ViewModel from INotifyPropertyChanged. I will a have List of Paths (PathList) stored in advance of starting the animation in my Model. At each (so called) time or animation step, I will copy the corresponding path from the PathList to the CurrentPath in the VieModel. I am hoping that change in the the CurrentPath collection in the ViewModel will activate the binding which will force the user control to update the tube drawn by the usercontrol.
These are my questions:
(1) I have read that not all changes to an ObservableCollection fires propertychanged events. Will overwriting or refereshing the whole CurrentPath collection in the ViewModel update the TubePath in the UserControl which will force redrawing of the tune? Do I have to do anything special to achieve this kind of binding.
(2) I am new to WPF and animations with WPF. My research indicated that I could do the animation from my ViewModel in several ways: using the Dispatcher.Invoke() like in the example given above, or I could use the RenderingEventManager.AddListener() (and RenderingEventManager.RemoveListener() to stop animation) provided by the Helix Toolkit like it is done in example here:
https://github.com/helix-toolkit/helix-toolkit/tree/develop/Source/Examples/WPF/ExampleBrowser/Examples/Wind
or I could loop using DispatcherTimer() as done here:
Binding on DependencyProperty of custom User Control not updating on change
Any suggestions as to the best method as well as my concept of driving animation from the ViewModel would be greatly appreciated.
I am working on wpf mvvm pattern. I have different user controls. Based on the checkbox selection, I want them to be loaded in the main screen (that is also a user control). I have one HomeViewModel class which I have been using to bind the user controls of my project. Can you help me with a suitable way?
You should have different ViewModels for each kinds of UserControl.
Create different DataTemplates for each ViewModel Types
Put a ContentControl with binding a property of HomeViewModel -
Value of property will be an instance of ViewModel ( UserControl's) and is set by toggling CheckBoxes.
I started playing around with Windows Phone development. I am using MVVM ligth and I am trying to follow good practices. But lately I ran into an issue:
Is it okay to use ViewModel inside a ViewModel as a property?
My scenario is that I am having a MainViewModel which is a Panorama object. This Panorama objects consists of few PanaoramaItems (Notes, Calender and About Controls/Pages).
My question is, if I have for the MainPage.xaml a MainViewModel, is it okay if I put the other ViewModels as properties (NotesViewModel, CalenderViewModel, AboutViewModel) to the MainViewModel, in that case those will inherit from the MainPage the DataContext and I would just bind to a property of the MainViewModel. Or should I rather use the locator pattern to allow the other pages/control to get their own ViewModels and do not inherit the DataContext?
Is it okay, if a control has a ViewModel or should it be rather for pages?
If the Parent and Child ViewModels are related: sure, that is fine, it does not violate the pattern.
This setup allows you to re-use ViewModels and Views across pages and controls.
i have a problem with WPF MVVM, i have one usercontrl loaded inside my main view.. And at my main view i have a status bar and one textbox. I want to change the text by clicking at button from usercontrol, how can i do that? I tried a lot os things here like raisedpropertiechange and nothing happens.
I have one ViewModel from MainModel and a lots of UserControls with theirs viewmodels. Each usercontrl viewmodel will have one button with need to be fired and change the text from parent Model.
Im not sure if im clear about this.
Regards
I would provide a command in the BaseClass of the UserControl viewmodel, which changes the text in the parent viewmodel of the UserControls viewmodel. The Buttons of the UserControl can bind to this command. And the title of the main view is bound to the text property.
Keep the views and controls as decoupled and 'stupid' as possible.
Then you only have to provide a reference of the main viewmodel in the other viewmodels.
I'm kinda new to WPF. I'm making an app using WPF (all the UI controls are already fixed) and MVVM but most of the events are in the code-behind. I'm in the process of clearing the code-behind but I have codes like (the ones below) to switch through tabs, and to trigger visibility of controls depending on parameters:
tabItem1.Selected = true;
textBox1.Visibility = Visibility.Hidden;
lbxHusbandsWives.Items.Add(txtHusbandsWives.Text + '/' +
cbxHusbandsWivesCountry.Text + '/' +
dpHusbandsWives.SelectedDate.Value.ToShortDateString());
How can I do that in the viewmodel? Well, inside a Command? So I can clear the messy code-behind? Thanks for your help. :)
As I said many times before, MVVM doesn't mean "no code behind". There are things that you can or should do in code-behind, as long as they are strictly related to the view and are not necessary for the ViewModel to work properly.
That being said, in most cases you don't need to do anything in code-behind. You normally use bindings to control the view from the ViewModel. This allows the ViewModel to be completely ignorant of the view: it just exposes properties that the view can access, and sends notifications when the values of the properties change. The ViewModel should definitely not manipulate the view or its components.
Everything in the code you posted can be done with bindings in XAML:
textBox1.Visibility can be bound to a bool property of the ViewModel, using a BooleanToVisibilityConverter
lbxHusbandsWives.ItemsSource can be bound to an ObservableCollection in the ViewModel (an ObservableCollection notifies the view when items are added to or removed from it)
txtHusbandsWives.Text, cbxHusbandsWivesCountry.Text and dpHusbandsWives.SelectedDate can also be bound to properties of the appropriate type