WPF binding Listbox SelectedItem in ViewModel

问题

I'm working on a WPF application. The main page is made up of a grid with 2 column and one row. on the first column i have a listbox and on the 2nd column i have a stackpanel named thePanel which i want to change on selected item of a listbox.i first implemented this in the View(mainwindow.xaml.cs) with the selectionChanged event of the Listbox and it worked. I tried to apply the MVVM so i had to do it in the viewModel. the Data Context of the mainwindow is set in its constructor and is of Type UserViewModel. The userViewModel has a property of Type ListBoxItem named SelectedItem which is bound in XAML to the SelectedItem of my listbox. Whenever that is changed, I go up in the UserViewModel with "Parent" until MainWindow and then remove all the children of thePanel and add what I want. The EntriesUC is an UserControl that takes the dataContext in the constructor parameter. There is no problem with it since it worked when i implemented SelectionChanged in the View. The problem is whenever I click any item of the listbox, nothing happens.

Main window:

<Window x:Class="SyntheticLTM.View.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:viewNamespace="clr-namespace:SyntheticLTM.View"
        Title="MainWindow" WindowState="Maximized" Height="350" Width="525">

    <StackPanel>
        //MENU IMPLEMENTATIOn

        <Grid>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="1*"/>
                <ColumnDefinition Width="4*"/>
            </Grid.ColumnDefinitions>

            <StackPanel Grid.Column="0">
                <Button Content="{Binding Name}" Width="84" />
                <ListBox Name="mainListBox" SelectionMode="Single" SelectedItem="{Binding SelectedItem, Mode=TwoWay}">
                    <ListBoxItem>Data entries</ListBoxItem>
                    <ListBoxItem>Categories</ListBoxItem>
                    <ListBoxItem>Favorites</ListBoxItem>
                    <ListBoxItem>Search</ListBoxItem>
                </ListBox>
            </StackPanel>

            <StackPanel Name="thePanel" Grid.Column="1"  />

        </Grid>
    </StackPanel>

</Window>

UserViewModel:

private ListBoxItem selectedItem;
 public ListBoxItem SelectedItem
            {
                get
                {
                    return selectedItem;
                }
                set
                {
                    selectedItem = value;
                    RaisePropertyChanged("SelectedItem");

                    var thePanel = new StackPanel();
                    thePanel=((((((selectedItem as ListBoxItem).Parent as ListBox).Parent as StackPanel).Parent as Grid).Parent as StackPanel).Parent as MainWindow).thePanel;
                    string message;
                    message = selectedItem.ToString();

                    if (message == "Data entries")
                    {
                        var allEntries = new CategoryViewModel();

                        foreach (var category in (thePanel.DataContext as UserViewModel).Categories)
                            allEntries.Entries = new ObservableCollection<EntryViewModel>(category.Entries);

                        thePanel.Children.Clear();
                        thePanel.Children.Add(new EntriesUC(allEntries));
                    }
// implementation for all the other list items...
                 }
               }

回答1:

Normally you wouldn't add ListBoxItems to the ListBox but you would directly add the strings and would work with a string as SelectedItem. The ListBox would wrap each string with a ListBoxItem automatically. But if you want to do it this way, you have to extract the selected string by

message = selectedItem.Content.ToString();

来源：https://stackoverflow.com/questions/26480975/wpf-binding-listbox-selecteditem-in-viewmodel

标签

wpf

xaml

mvvm

listbox