C#•3y ago

❔ ❔ Bind selected items

In my MVVM, I have connected view and viewModel to display "Months" list, but not sure how to bind and send through selected ones. Could anyone help me with binding?

15 Replies

dancepanda42•3y ago

Did you set the ViewModel to the DataContext of your View? like this:

public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            DataContext = new MainWindowViewModel();
        }
    }

public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            DataContext = new MainWindowViewModel();
        }
    }

edgarka_OP•3y ago

Yes -

dancepanda42•3y ago

ok, the ItemsTemplate is unnecessary the listbox can manage text alone

edgarka_OP•3y ago

They are populated, but I'd like to send selected to the model

dancepanda42•3y ago

You can make a additional property like: public string SelectedItem {get; set:} and bind the Listbox propertye SelectedItem to it. Then the property in the ViewModel will have the value of the selection from the Listbox another hint, initialize your list in the constuctor. Then return the private field _month in the getter of the property. Instead of creating a new list each time.

edgarka_OP•3y ago

Thank you @dancepanda42, I've added property and it grabs string properly Is it possible to send it as list, considering I have a multiple selection?

dancepanda42•3y ago

yes, but this requires a little more code.

<ListBox ItemsSource="{Binding Items}" SelectionMode="Multiple" >
    <ListBox.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding DisplayText}" />
        </DataTemplate>
    </ListBox.ItemTemplate>
    <ListBox.ItemContainerStyle>
        <Style TargetType="ListBoxItem">
            <Setter Property="IsSelected"
                    Value="{Binding IsSelected}" />
        </Style>
    </ListBox.ItemContainerStyle>
</ListBox>

<ListBox ItemsSource="{Binding Items}" SelectionMode="Multiple" >
    <ListBox.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding DisplayText}" />
        </DataTemplate>
    </ListBox.ItemTemplate>
    <ListBox.ItemContainerStyle>
        <Style TargetType="ListBoxItem">
            <Setter Property="IsSelected"
                    Value="{Binding IsSelected}" />
        </Style>
    </ListBox.ItemContainerStyle>
</ListBox>

public partial class MainWindowViewModel : ObservableObject
{
    private List<SelectableItem> _items;
    public List<SelectableItem> Items
    {
        get => _items;
        set
        {
            _items = value;
            OnPropertyChanged(nameof(Items));
        }
    }

    public MainWindowViewModel()
    {
        _items = new List<SelectableItem>
        {
            new SelectableItem { DisplayText = "Entry01"},
            new SelectableItem { DisplayText = "Entry02"},
            new SelectableItem { DisplayText = "Entry03"},
            new SelectableItem { DisplayText = "Entry04"},
        };
    }
}

public class SelectableItem : ObservableObject
{
    private string _displayText;
    public string DisplayText
    {
        get => _displayText;
        set
        {
            _displayText = value;
            OnPropertyChanged(nameof(_displayText));
        }
    }

    private bool _isSelected;
    public bool IsSelected
    {
        get => _isSelected;
        set
        {
            _isSelected = value;
            OnPropertyChanged(nameof(_isSelected));
        }
    }
}

public partial class MainWindowViewModel : ObservableObject
{
    private List<SelectableItem> _items;
    public List<SelectableItem> Items
    {
        get => _items;
        set
        {
            _items = value;
            OnPropertyChanged(nameof(Items));
        }
    }

    public MainWindowViewModel()
    {
        _items = new List<SelectableItem>
        {
            new SelectableItem { DisplayText = "Entry01"},
            new SelectableItem { DisplayText = "Entry02"},
            new SelectableItem { DisplayText = "Entry03"},
            new SelectableItem { DisplayText = "Entry04"},
        };
    }
}

public class SelectableItem : ObservableObject
{
    private string _displayText;
    public string DisplayText
    {
        get => _displayText;
        set
        {
            _displayText = value;
            OnPropertyChanged(nameof(_displayText));
        }
    }

    private bool _isSelected;
    public bool IsSelected
    {
        get => _isSelected;
        set
        {
            _isSelected = value;
            OnPropertyChanged(nameof(_isSelected));
        }
    }
}

To clarify. The SelectableItem gets the information that it is selected from the ListBoxItem through the binding in the style. To display the values, another property is now needed in the SelectableItem. This can also be displayed by an ItemTemplate via a binding. This example should work

edgarka_OP•3y ago

I'll give it a go ObservableObject is part of some external package?

dancepanda42•3y ago

yes its form the CommunityToolkit.Mvvm makes it more comfortable to write the mvvm pattern. but you can also use your ViewModelBase

edgarka_OP•3y ago

Binding now works, thank you!

dancepanda42•3y ago

your welcome

edgarka_OP•3y ago

I'll try to play around for a bit, bind to models, would it be okay if I'll keep question open for some time and ask you if I'm stuck?

dancepanda42•3y ago

sure am but in the Berlin time zone... so I'm no longer so long online. but you can send me a PM then I answer as soon as I find time.

edgarka_OP•3y ago

Thank you @dancepanda42 🙂

Accord•3y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity. Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ ❔ Bind selected items

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