I have a combobox in my XAML:
<ComboBox Name="MyComboBox" />
I want to bind the whole object to a property in my view class:
public class MyView : INotifyPropertyChanged
{
public ComboBox MyComboBox;
...
}
I know how to bind individual properties of the combobox to a property in my view class but is there a way to bind the whole element? I only need two properties so I could just bind the two properties separately but wanted to know if there is a way to do it in one shot.
Related
I'm writing WPF application with MVVM structure using MVVM Light.
I have class Foo in the Model:
class Foo: ObservableObject
{
private string _propA = String.Empty;
public string PropA
{
get => _propA ;
set
{
if (_propA == value)
{
return;
}
_propA = value;
RaisePropertyChanged("PropA");
}
}
// same for property PropB, PropC, PropD, etc.
}
And I have some collection of Foo objects in the Model:
class FooCollection: ObservableObject
{
private ObservableCollection<Foo> _items = null;
public IEnumerable<Foo> Items
{
get { ... }
set { ... }
}
public string Name { get; set; }
// ...
// and other methods, properties and fields
}
Now I have a ViewModel where this list is populated via some injected provider:
class MainWindowModel: ViewModelBase
{
private FooCollection _fooList;
public FooList
{
get => _fooList;
set
{
_fooList = value;
RaisePropertyChangedEvent(FooList);
}
}
public MainWindowModel(IFooListProvider provider)
{
FooList = provider.GetFooList();
}
}
And the View, with MainWindowModel as data context:
<TextBlock Text={Binding FooList.Name} />
<ItemsControl ItemsSource="{Binding FooList.Items}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBlock Text={Binding PropA} />
<Button Content={Binding PropB} />
<!-- other controls with bindings -->
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
Everything works fine, I can delete and add new items, edit them and etc. All changes in View reflects automatically in ViewModel and Model via bindings and observable objects, and vice versa.
But now I need to add ToggleButton to data template of ItemsControl, which controls visibility of particular item in other part of window. I need IsChecked value in ViewModel, because control in other part of window is Windows Forms control and I can't bind IsChecked directly without ViewModel.
But I don't want to add new property (Visibility, for example) in model classes (Foo, FooCollection), because it is just an interface thing and it doesn't need to be saved or passed somewhere outside ViewModel.
So my question: what is the best way to add new property to Model collection in ViewModel?
I could create new collection of wrappers in ViewModel (some sort of class Wrapper { Foo item, bool Visibility }) and bind it to ItemsControl. But in this case I have to control adding, removing and editing manually and transfer all changes from List<Wrapper> to FooList.Items, so I don't like this solution. Is there any more simple way to achieve this?
Edition to clarify the question. Now I have:
<ItemsControl ItemsSource="{Binding FooList.Items}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBlock Text={Binding PropA} />
<Button Content={Binding PropB} />
<ToggleButton IsChecked={Binding ????????????} />
<!-- other controls with bindings -->
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
I have no field in class to bind IsChecked and I don't want to add it to class, because it's only interface thing and not data model field. How can I, for example, create another collection of bools and bind it to this ItemControl alongside with FooList.Items?
The best place to add the property is of course in the Foo class.
Creating another collection of some other type, add an object per Foo object in the current collection to this one, and then bind to some property of this new object seems like a really bad solution compared to simply adding a property to your current class.
Foo is not an "interface thing", or at least it shouldn't be. It is view model that is supposed to contain properties that the view binds to. There is nothing wrong with adding an IsChecked property to it. This certainly sounds like the best solution in your case.
I'm not sure if I understand why you would need to add a property in the model.
Can't you just use the command property or add an EventTrigger to your toggle button?
(See Sega and Arseny answer for both examples Executing a command on Checkbox.Checked or Unchecked )
This way, when you check the toggleButton, there is a method in your viewModel which enable or disable the visibility property of your Winform control.
To change the visibility of your control from a command in your viewModel, you could use the messenger functionnality of MVVM LIGHT
MVVM Light Messenger - Sending and Registering Objects
The ViewModel sends a message to you're Windows Forms and this one handles the visibility of your control.
I have a BlogStore class which contains two observablecollections like so
public class BlogStore {
public ObservableCollection<Blog> blogs ...
public ObservableCollection<Blog> favourites ...
}
public BlogStore blogStore ...
no I want to reuse a control which does the following binding
ItemsSource="{Binding blogStore.blogs}
so that I can switch to favourites, the following does not work, but I would like something in a similar vein.
ItemsSource={Binding blogStore{Binding category, ElementName=blogControl}
and in the controls code behind i would have a dependency property.
maybe a converter could do the trick?
If you treat BlogStore as a ViewModel then it would expose a couple of other properties.
Category to which you bind what ever control you are using to choose the category to display.
Also a CategoryBlogs property which returns either the value of blogs or favourites depending on the value of Category.
You would be implementing INotifyPropertyChanged so you would ensure that a PropertyChanged event is fired for "CategoryBlogs" when the Category property is changed.
You would be binding ItemsSource just to CategoryBlogs.
I have an image inside a user control that I want to bind it's visibility to a property I have set up in a class object. The dependency properties are set up and working correctly, but I don't know how to set the binding properly on the image.
The user control and class object are in the same namespace. I thought I would need to set the ElementName to the window or the RelativeSource to the class object, but I'm not getting it to work out.
Here's what a dependency property looks like (defined in MigrateUserWizardObject.cs, this inherits from DependencyObject, this resides in the UserAccountMigrator namespace):
public static readonly DependencyProperty DatabaseStepCompletedVisibilityProperty = DependencyProperty.Register("DatabaseStepCompletedVisibility", typeof(Visibility), typeof(MigrateUserWizardObject));
public Visibility DatabaseStepCompletedVisibility
{
get
{
return (Visibility)GetValue(DatabaseStepCompletedVisibilityProperty);
}
set
{
SetValue(DatabaseStepCompletedVisibilityProperty, value);
}
}
Here's an image that I want bound to this dependency property (defined in ProgressUserControl.xaml, this inherits from UserControl, this resides in the UserAccountMigrator namespace as well):
<Image x:Name="DatabaseCompleted" Source="{StaticResource GreenCheckMarkSource}" Visibility="{Binding Path=DatabaseStepCompletedVisibility, UpdateSourceTrigger=PropertyChanged}" Height="20" HorizontalAlignment="Right"></Image>
This is due to the fact that the DataContext of the image is the user control. How can I make this work?
I think you should look into using the Model-View-ViewModel pattern. Instead of setting the DataContext to the UserControl, set it to an instance of another class (ProgressViewModel, for example). This view model would have all the properties you want to bind to (including your DatabaseStepCompletedVisibility property) and makes it much easier. Right now you are wanting to bind some things to the UserControl, some things to another object somewhere else, etc.. and, as you have found, makes it difficult. Here is more information:
http://jmorrill.hjtcentral.com/Home/tabid/428/EntryId/432/MVVM-for-Tarded-Folks-Like-Me-or-MVVM-and-What-it-Means-to-Me.aspx
Without going that approach, you have to have an instance MigrateUserWizardObject to bind to. You can put that instance in your UserControl (if you insist on using it as the DataContext), then you can bind the the property of the MigrateUserWizardObject property of the UserControl. Also, your MigrateUserWizardObject doesn't have to be a dependency object or dependency property to bind to. A better pattern would be to make it a plain c# class that implements the INotifyPropertyChanged interface.
i have three listboxes, whose itemsSource is binded to a list, list and dictionary. i want to add the selected user and selected book to the dictionary with a command but i can't take the selected items. i am trying to obey the mvvm. i have a booklist and a userlist in my viewmodel which are binded to the given listboxes in my view. i couldn't send the selected items to my viewmodel. how can i do this?
thanks for helping in advance.
Just bind a property to SelectedItem:
<ListBox
ItemsSource="{Binding Books}"
SelectedItem="{Binding SelectedBook}"/>
And in the ViewModel
public class Library : INotifyPropertyChanged
{
public ObservableCollection<Book> Books {get;private set;}
public Book SelectedBook {get;set;}
}
In your viewModel, couldn't you create a SelectedBook and a SelectedUser and bind those to the SelectedItem of your ListBoxes? Then, when they change, add them to your dictionary.
You can also use standard binding syntax using a slash (/).
{Binding Books/}
will allow you to bind directly to the current item in a collection.
Working with the MVVM pattern, I have a pair of view model classes that represent a two-tier data hierarchy, each with a corresponding UserControl that represents its view. Both view model classes implement INotifyPropertyChanged and the root level view model exposes a property that is relevant to both its own view and the child view.
The root level view acquires the root level view model as its data context and explicitly assigns a data context to its contained view. However, it also needs to bind one of the properties of the child view to the above-mentioned shared property. Here is how I have attempted to achieve this, but it's not working:
<UserControl x:Name="rootView">
<StackPanel>
<!-- other controls here -->
<my:ChildView
DataContext="{Binding Path=SelectedChild}"
EditingMode="{Binding ElementName=rootView, Path=DataContext.EditingMode />
</StackPanel>
</UserControl>
Although there are no runtime binding errors and the child view correctly binds to the appropriate child view model instance, its EditingMode property is never set. I have run tests to verify that the corresponding view model property is being modified and that it is notifying this change via INotifyPropertyChanged, but the binding fails to detect it.
Is there a better way to declare this binding or have I made a more basic architectural error?
Many thanks for your advice,
Tim
Update: As requested, I am posting some code to show a very simplified version of my views and view models, together with the results of an experiment that I have conducted that may provide some additional clues.
// The relevant parts of the ParentViewModel class
public class ParentViewModel : INotifyPropertyChanged
{
// Although not shown, the following properties
// correctly participate in INotifyPropertyChanged
public ChildViewModel SelectedChild { get; private set; }
public ContentEditingMode EditingMode { get; private set; }
}
// The relevant parts of the ChildViewModel class
public class ChildViewModel : INotifyPropertyChanged
{
// No properties of ChildViewModel affect this issue.
}
// The relevant parts of the ParentView class
public partial class ParentView : UserControl
{
// No properties of ParentView affect this issue.
}
// The relevant members of the ChildView class
public partial class ChildView : UserControl
{
public static readonly DependencyProperty EditingModeProperty =
DependencyProperty.Register(
"EditingMode",
typeof(ContentEditingMode),
typeof(PostView)
);
public ContentEditingMode EditingMode
{
get { return (ContentEditingMode)GetValue(EditingModeProperty); }
set { SetValue(EditingModeProperty, value); }
}
}
// The enumeration used for the EditingMode property
public enum ContentEditingMode
{
Html,
WYSYWIG
}
My intention is that the DataContext of the parent view instance will be assigned an instance of ParentViewModel and it will, in turn, assign the value of its SelectedChild property to the DataContext of the nested ChildView. All of this seems to work correctly, but the problem arises because the binding between ParentViewModel.EditingMode and ChildView.EditingMode does not work.
In an attempt to test whether there is a problem with my binding expression, I introduced a TextBlock adjacent to the ChildView and bound it similarly to the ParentViewModel.EditingMode property:
<UserControl x:Name="rootView">
<StackPanel>
<!-- other controls here -->
<TextBlock Text="{Binding ElementName=rootView, Path=DataContext.EditingMode}" />
<my:ChildView
DataContext="{Binding Path=SelectedChild}"
EditingMode="{Binding ElementName=rootView, Path=DataContext.EditingMode />
</StackPanel>
</UserControl>
In this test, the TextBlock is correctly updated every time the source property changes. However, if I set a breakpoint on the setter of ChildView.EditingMode, it never gets hit.
I'm baffled !
The simplest way to fix this is in your view model. Implement an EditingMode property in the child view model and bind to it. That way, you don't have to make any kind of guesses about what the right way to establish the binding might be; also, it's something that you can test outside of the UI.
Edit
Actually the right solution is not quite as simple, but it's worth knowing how to do.
What you want is for EditingMode in the child control to efficiently inherit its value from the parent control. Does that sound like something that anything else in WPF does? Like just about every framework element that implements dependency properties?
Implement EditingMode as a dependency property in both the parent and child UserControls and use property value inheritance, as described here. That takes the inheritance behavior out of the view model entirely and puts it where it belongs.
See if you can just use a full path to get the editing mode of the selected child:
<my:childView
DataContext="{Binding SelectedChild}"
EditingMode="{Binding SelectedChild.EditingMode />