How to bind a list(of string) on a combobox via Binding-CodePudding

I can't bind a list (of string) as the source of a combobox via Binding. It works with

cb_ListTexts.ItemsSource = cKiosque.ListTexts

but not with

cb_ListTexts.DataContext = cKiosque

<Window x:Class="MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:BindingWPF"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <ComboBox x:Name="cb_ListTexts"  SelectedValue="{Binding Path=ckiosque.ListTexts}" HorizontalAlignment="Left" Height="51" Margin="97,121,0,0" VerticalAlignment="Top" Width="367"/>
        <TextBox x:Name="tb_SelectedItem" Text="{Binding Path=SelectedValue, ElementName=cb_ListTexts}"  HorizontalAlignment="Left" Height="28" Margin="243,235,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="288"/>
    </Grid>
</Window>

Imports System.ComponentModel

Class MainWindow

    Private Property cKiosque As New Kiosque

    Sub New()
        ' Cet appel est requis par le concepteur.
        InitializeComponent()

        ' Ajoutez une initialisation quelconque après l'appel InitializeComponent().
        cb_ListTexts.DataContext = cKiosque.ListTexts
        'cb_ListTexts.ItemsSource = cKiosque.ListTexts
    End Sub

End Class

Class Kiosque

    Implements INotifyPropertyChanged
    Public Event PropertyChanged(sender As Object, e As PropertyChangedEventArgs) Implements INotifyPropertyChanged.PropertyChanged

    Private Property _ListTexts As New List(Of String)
    Private Property _SelectedItem As String

    Sub New()
        ListTexts.Add("toto")
        ListTexts.Add("titi")
    End Sub

    Public Sub OnPropertyChanged(ByVal e As PropertyChangedEventArgs)
        If Not PropertyChangedEvent Is Nothing Then
            RaiseEvent PropertyChanged(Me, e)
        End If
    End Sub

    Public Property ListTexts As List(Of String)
        Get
            Return _ListTexts
        End Get
        Set(value As List(Of String))
            _ListTexts = value
            'OnPropertyChanged(New PropertyChangedEventArgs("ListTexts"))
        End Set
    End Property

    Public Property SelctedItem As String
        Get
            Return _SelectedItem
        End Get
        Set(value As String)
            _SelectedItem = value
        End Set
    End Property

End Class

Where is the error ?

CodePudding user response：

DataContext is different from ItemsSource. Exemple : You set your Grid DataContext to point to your Kiosque. Then, each child and subchilds will inherit their DataContext from your Grid (cascading).

Now, if a binding is found, it will try to apply a binding to a matching property name from the {Binding Path=MyProperty} in your Kiosque object (known as a ViewModel)

To debug, I suggest you to set this.DataContext = Kiosque. In the constructor of your window. Thus, no need to set DataContext.

Try with something like

<Grid>
    <ComboBox SelectedItem="{Binding SelctedItem}" ItemsSource="{Binding ListTexts}" HorizontalAlignment="Left" Height="51" Margin="97,121,0,0" VerticalAlignment="Top" Width="367"/>
    <TextBox Text="{Binding Path=ListTexts}"  HorizontalAlignment="Left" Height="28" Margin="243,235,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="288"/>
</Grid>

Be careful : you typed SelctedItem instead of SelectedItem. You don't need to use SelectedValue because you are binding a string. Selected value is to bind to a sub property of the item (eg : Engine to display the engine of SelectedCar.Engine)

CodePudding user response：

It works! Thanks for your help