Listbox in WPF: Items collection must be empty before using ItemsSource

Question

I'm having some issues with the ItemsSource property in WPF (for binding). I can't run my program while having the "ItemsSource="{Binding}" as a property for my ListBox. Although, if I remove it, the program runs fine but the binding doesn't work.

XAML:

<Window x:Class="TP1.EcranPrincipal"
        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:TP1"
        mc:Ignorable="d"
        Background="CornflowerBlue"
        Title="" Height="400" Width="700">

    <Window.Resources>
        <DataTemplate x:Key="masterTemplate">
            <TextBlock
          Margin="4"
          Text="{Binding Description,UpdateSourceTrigger=PropertyChanged}"/>
        </DataTemplate>
    </Window.Resources>

    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="2*"/>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="2*"/>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="2*"/>
        </Grid.ColumnDefinitions>

        <Grid.RowDefinitions>
            <RowDefinition Height="*"/>
            <RowDefinition Height="*"/>
            <RowDefinition Height="*"/>
            <RowDefinition Height="*"/>
            <RowDefinition Height="*"/>
            <RowDefinition Height="*"/>
            <RowDefinition Height="*"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>

        <TextBox Grid.Column="1" Grid.Row="0" Padding="5" VerticalContentAlignment="Center" Margin="10,10,90,0" TextWrapping="NoWrap" Text="" VerticalAlignment="Top" Grid.ColumnSpan="4"/>
        <Button x:Name="BoutonRechercher" Grid.Column="4" Grid.Row="0" Padding="5" Content="Rechercher" HorizontalAlignment="Left" Margin="88,9,0,0" VerticalAlignment="Top" Click="BoutonRechercher_Click" Width="75"/>

        <!-- 1st TextBoxes' column -->
        <TextBox x:Name="Nom" Text="{Binding Nom,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Grid.Column="2" Grid.Row="1" Margin="0, 0, 10, 10" VerticalContentAlignment="Center"/>
        <TextBox x:Name="Telephone" Text="{Binding Téléphone,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Grid.Column="2" Grid.Row="2" Margin="0, 0, 10, 10"  VerticalContentAlignment="Center" Padding="5,0" />
        <TextBox x:Name="Adresse1" Text="{Binding Adresse1,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Grid.Column="2" Grid.Row="3" Margin="0, 0, 10, 10" Grid.ColumnSpan="3" VerticalContentAlignment="Center"/>
        <TextBox x:Name="Adresse2" Text="{Binding Adresse2,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Grid.Column="2" Grid.Row="4" Margin="0, 0, 10, 10" Grid.ColumnSpan="3" VerticalContentAlignment="Center"/>
        <TextBox x:Name="Ville" Text="{Binding Ville,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Grid.Column="2" Grid.Row="5" Margin="0, 0, 10, 10" VerticalContentAlignment="Center"/>
        <TextBox x:Name="Pays" Text="{Binding Pays,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Grid.Column="2" Grid.Row="6" Margin="0, 0, 10, 10" VerticalContentAlignment="Center"/>

        <!-- 2nd TextBoxes' column -->
        <TextBox x:Name="Prenom" Text="{Binding Prénom,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Grid.Column="4" Grid.Row="1" Margin="0, 0, 10, 10" VerticalContentAlignment="Center"/>
        <TextBox x:Name="Courriel" Text="{Binding Courriel,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Grid.Column="4" Grid.Row="2" Margin="0, 0, 10, 10" VerticalContentAlignment="Center"/>
        <TextBox x:Name="Province" Text="{Binding Province,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Grid.Column="4" Grid.Row="5" Margin="0, 0, 10, 10" VerticalContentAlignment="Center"/>
        <TextBox x:Name="CodePostal" Text="{Binding CodePostal,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Grid.Column="4" Grid.Row="6" Margin="0, 0, 10, 10" VerticalContentAlignment="Center"/>

        <ListBox x:Name="ListeBoxUtilisateurs" ItemsSource="{Binding}" ItemTemplate="{StaticResource masterTemplate}" IsSynchronizedWithCurrentItem="True" HorizontalAlignment="Left" Height="349" Margin="10,10,0,0" VerticalAlignment="Top" Width="153" Grid.RowSpan="7"/>


    </Grid>
</Window>

C#:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;

// StreamReader/Writer:
using System.IO;
using System.ComponentModel;

namespace TP1
{
    /// <summary>
    /// Logique d'interaction pour EcranPrincipal.xaml
    /// </summary>
    public partial class EcranPrincipal : Window
    {

        // Required variables to read the file
        List<String> elementsLignes = new List<String>();
        List<Utilisateur> utilisateurs = new List<Utilisateur>();
        Collection Coll = new Collection();



        public EcranPrincipal()
        {
            InitializeComponent();
            this.DataContext = Coll;
            ListBox listeUtilisateurs = ListeBoxUtilisateurs;

            var reader = new StreamReader(File.OpenRead("TextFile.txt"));
            int nbUtilisateurs = 0;

            Console.WriteLine(reader.ReadLine());

            while (reader.ReadLine() != null)
            {
               // Reading the file, this works fine
            }
        }


        private ListBoxItem selectedItem;
        public ListBoxItem SelectedItem
        {
            get { return selectedItem; }
            set { selectedItem = value; }
        }
    }
}

Everytime I run my program, I get this Items collection must be empty before using ItemsSource error. Anyone figured out what my problem is?

Answer 1

Your Bindings seem off, in my opinion.

1. you are declaring that the DataContext shall be an empty Coll - maybe you just dropped the code.
2. You should set the DataContext before the call InitializeComponent() to prevent heavy - unnecessary - DataContextChanged Event handling
3. Your TextBoxes than bind to that DataContext - why should a Collection have properties like Nom, Téléphone and so on
4. Why do you have the member SelectedItem when you never use it?

I would recommend the following members in your window:

public ObservableCollection<object> Coll { get; set; }
public object SelectedItem { get; set; }

(Change object to your actualy type you have)

Maybe - maybe because I cannot tell if the properties are inside the object of the listview or not - change all your TextBoxes to have the following binding:

<TextBox x:Name="Nom" Text="{Binding SelectedItem.Nom, UpdateSourceTrigger=PropertyChanged}" />

Change your ListBox to this:

<ListBox x:Name="ListeBoxUtilisateurs" ItemsSource="{Binding Coll}" SelectedItem="{Binding SelectedItem}" ItemTemplate="{StaticResource masterTemplate}" HorizontalAlignment="Left" Height="349" Margin="10,10,0,0" VerticalAlignment="Top" Width="153" Grid.RowSpan="7"/>