设置UserControl可见性

Question

I have a property that is not binding and cannot figure out where the problem is. Can someone please help? My Converter is running for other bound controls, so there is no issue there. When setting a break point, I never see the property IsMyControlVisible get hit.

I added this line to the property MyControlViewModels:

this.NotifyPropertyChanged(m => m.IsMyControlVisible); 

When it get hit, it causes the set of my property to be hit, but nothing happens with the visibility of my control, even though I can see the value is true. The control is completely functional, I just cannot get it to show programmatically. Also, my visibility converter works for other views, so that is not the problem.

It seems (to me) that the binding is just not set up correctly and if I can get it working, the visibility would work on the control.

My control is inside a TabControl, which is inside a Grid on my view.

I've found this post that was the closest to my problem and tried it without success:

UserControl Visibility binding through ViewModel

ConfigurationEditorView.xaml:

<ctrls:MyControl Grid.Row="0" 
    Visibility="{Binding Path=IsMyControlVisible, 
    Converter={StaticResource booleanToStringConverter},
    FallbackValue=Hidden}" />

ConfigurationEditorView's Constructor:

this.DataContext = new ConfigurationEditorViewModel();

ConfigurationEditorViewModel:

public bool IsMyControlVisible
{
    get
    {
        return this.MyControlViewModels.Count > 0;
    }
}

private ObservableCollection<MyControlViewModel> myControlViewModels 
    = new ObservableCollection<MyControlViewModel>();

public ObservableCollection<MyControlViewModel> MyControlViewModels
{
    get
    {
        return this.myControlViewModels;
    }

    set
    {
        this.myControlViewModels = value;

        this.NotifyPropertyChanged(m => m.myControlViewModels);

        this.NotifyPropertyChanged(m => m.IsMyControlVisible);
    }
}

ConfigurationEditorViewModel Constructor:

public ConfigurationEditorViewModel()
{
    this.MyControlViewModels.Add(new MyControlViewModel);
}

Answer 1

您正在使用boolToString转换器，并且您实际上需要可见性。

Answer 2

As your code is written, you'll only get a notification if someone assigns a new instance of ObservableCollection to your MyControlViewModels property. Instead, in the setter, you would write wherever you create your view models, you would add

set
{
    if (myControlViewModels != null)
    {
        myControlViewModels.CollectionChanged -= OnControlViewModelsChanged;
    }

    this.myControlViewModels = value;

    this.NotifyPropertyChanged(m => m.IsMyControlVisible);

    if (myControlViewModels != null)
    {
        myControlViewModels.CollectionChanged += OnControlViewModelsChanged;
    }
}

where

public void OnControlViewModelsChanged(object sender, NotifyCollectionChangedEventArgs e)
{
    this.NotifyPropertyChanged(m => m.IsMyControlVisible);
}

Another minor point: normally you would not have a setter for a property of type ObservableCollection - it would be get-only, and you would create it in the constructor. That would simplify some of your code (like not needing to unsubscribe from the change event). See for instance ItemsControl.Items (it doesn't use an observable collection, the pattern is the same).

Answer 3

There is a BooleanToVisibilityConverter you can you use. The value you are trying to get is an enum called Visibility, not a string.