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:

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
{
    /// 
    /// Logique d'interaction pour EcranPrincipal.xaml
    /// 
    public partial class EcranPrincipal : Window
    {

        // Required variables to read the file
        List elementsLignes = new List();
        List utilisateurs = new List();
        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?

Rand Random · Accepted Answer

Your Bindings seem off, in my opinion.

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

I would recommend the following members in your window:

public ObservableCollection

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

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