C# – WPF Disable listbox items with MVVM

cdatatriggerlistboxmvvmwpf

I tried searching through a lot of threads and I've found several that's pretty close but not exactly what I want. After a day of searching, I just decided to ask. Apologies if I missed something, I feel like this would be common enough but I can't seem to quite get it.

I have UserControl that bounded to a ViewModel, and it has a Listbox with ItemsSource=ObservableCollection which is a property of the ViewModel like below:

Whenever I select an item, I call SomeObject.IsEnabled = false on several other items depending on certain conditions. I'd like to bind the listbox items to that IsEnabled property so I can grayout whichever items whenever I do a selection.

ViewModel:

Class ViewModel : PropertyNotificationObject
{
    private ObservableCollection<SomeObject> m_list;
    public ObservableCollection<SomeObject> List {get; set;} //notifying properly

    private void selectedItem()
    {
        //several in SomeObjects in List sets IsEnabled = false
    }
}

The Object Class

class SomeObject : PropertyNotificationObject
{
   private bool m_isEnabled;
   public IsEnabled { get; set; } //notifying properly
}

XAML

 <DataTemplate x:Key="ListTemplate">
    <Grid>
       <Grid.ColumnDefinitions>
          <ColumnDefinition Width="*"/>
       </Grid.ColumnDefinitions>
       <TextBlock Text="{Binding ., Converter={someConverterObjectToString}}"/>
    </Grid>
 </DataTemplate>
 <ListBox ItemsSource="{Binding List}" ItemTemplate="{StaticResource ListTemplate}"/>

I've tried using StyleTriggers in the ListBox.ItemContainerStyle and the DataTemplate like below but I couldn't figure out how to get to the SomeOject.IsEnabled property.

<ListBox.ItemContainerStyle>
    <Style TargetType="{x:Type ListBoxItem}">
        <Style.Triggers>
            <DataTrigger Binding={???????? I can't get to my SomeObject properties.}
        </Style.Triggers>
    </Style>
</ListBox.ItemContainerStyle>

Sorry for the lack of colors, I'm new here and don't really know how use the editor very well.

Thanks in advance.

Best Answer

{Binding IsEnabled} in your ItemContainerStyle should do the work. Look at VS debug window for binding errors

Edit or directly bind the IsEnabled property of the ListBoxItem:

<Style TargetType="{x:Type ListBoxItem}">
    <Setter Property="IsEnabled" Value="{Binding IsEnabled}"/>
</Style>

Related Solutions

C# – Binding a WPF ComboBox to a custom list

You set the DisplayMemberPath and the SelectedValuePath to "Name", so I assume that you have a class PhoneBookEntry with a public property Name.

Have you set the DataContext to your ConnectionViewModel object?

I copied you code and made some minor modifications, and it seems to work fine. I can set the viewmodels PhoneBookEnty property and the selected item in the combobox changes, and I can change the selected item in the combobox and the view models PhoneBookEntry property is set correctly.

Here is my XAML content:

<Window x:Class="WpfApplication6.Window1"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Window1" Height="300" Width="300">
<Grid>
    <StackPanel>
        <Button Click="Button_Click">asdf</Button>
        <ComboBox ItemsSource="{Binding Path=PhonebookEntries}"
                  DisplayMemberPath="Name"
                  SelectedValuePath="Name"
                  SelectedValue="{Binding Path=PhonebookEntry}" />
    </StackPanel>
</Grid>
</Window>

And here is my code-behind:

namespace WpfApplication6
{

    /// <summary>
    /// Interaction logic for Window1.xaml
    /// </summary>
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();
            ConnectionViewModel vm = new ConnectionViewModel();
            DataContext = vm;
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            ((ConnectionViewModel)DataContext).PhonebookEntry = "test";
        }
    }

    public class PhoneBookEntry
    {
        public string Name { get; set; }

        public PhoneBookEntry(string name)
        {
            Name = name;
        }

        public override string ToString()
        {
            return Name;
        }
    }

    public class ConnectionViewModel : INotifyPropertyChanged
    {
        public ConnectionViewModel()
        {
            IList<PhoneBookEntry> list = new List<PhoneBookEntry>();
            list.Add(new PhoneBookEntry("test"));
            list.Add(new PhoneBookEntry("test2"));
            _phonebookEntries = new CollectionView(list);
        }

        private readonly CollectionView _phonebookEntries;
        private string _phonebookEntry;

        public CollectionView PhonebookEntries
        {
            get { return _phonebookEntries; }
        }

        public string PhonebookEntry
        {
            get { return _phonebookEntry; }
            set
            {
                if (_phonebookEntry == value) return;
                _phonebookEntry = value;
                OnPropertyChanged("PhonebookEntry");
            }
        }

        private void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
        public event PropertyChangedEventHandler PropertyChanged;
    }
}

Edit: Geoffs second example does not seem to work, which seems a bit odd to me. If I change the PhonebookEntries property on the ConnectionViewModel to be of type ReadOnlyCollection, the TwoWay binding of the SelectedValue property on the combobox works fine.

Maybe there is an issue with the CollectionView? I noticed a warning in the output console:

System.Windows.Data Warning: 50 : Using CollectionView directly is not fully supported. The basic features work, although with some inefficiencies, but advanced features may encounter known bugs. Consider using a derived class to avoid these problems.

Edit2 (.NET 4.5): The content of the DropDownList can be based on ToString() and not of DisplayMemberPath, while DisplayMemberPath specifies the member for the selected and displayed item only.

WPF ListBox ItemsSource with DataTemplate

<TextBlock Text="{Binding Path=(Description)}" />

Why do you have parens in there? This syntax causes WPF to try to bind to an attached property, which is not what you want to do.

Best Answer

Related Solutions

C# – Binding a WPF ComboBox to a custom list

WPF ListBox ItemsSource with DataTemplate

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