C#•9mo ago

❔ ✅ WinForms ListBox.DataSource not working

I have a ListBox that contains only instances of Employee. ToString looks like Employee { Name: "John Smith", Id: 123, Salary: $100,000.00 }. Without creating my own list and instead just adding objects to the ObjectCollection already owned by the ListBox, everything works. When I create my own list public List<Employee> _employees and initialize it before the components of the form and set the ListBox data source after the components in the form constructor, no values from the list are shown. I am refreshing the ListBox in its prompt closing event after adding the Employee to the list. Looking online did not help since they all said to do what I thought I needed to do to bind a ListBox in the first place, which is to just set the data source using the appropriate object or refreshing the list. Here's the relevant code:

public partial class Form1 : Form
{
    private List<Employee> _employees;
    public Form1()
    {
        _employees = new();
        InitializeComponent();
        EmployeesListBox.DataSource = _employees;
    }

    private void CreateEmployeeButton_Click(object sender, EventArgs e)
    {
        var employee = new Employee();
        var prompt = new EmployeeCreatorForm(employee);
        prompt.Closing += (_, _) => // No leaking since prompt is closing
        {
            if (!prompt.Completed)
                return;

            _employees.Add(employee);
            Show();
            EmployeesListBox.Refresh();
        };

        Hide();
        prompt.Show();
    }

    private void CreateManagerButton_Click(object sender, EventArgs e)
    {
        var manager = new Manager();
        var prompt = new ManagerCreatorForm(manager);
        prompt.Closing += (_, _) =>
        {
            if (!prompt.Completed)
                return;

            _employees.Add(manager);
            Show();
            EmployeesListBox.Refresh();
        };

        Hide();
        prompt.Show();
    }
}

public partial class Form1 : Form
{
    private List<Employee> _employees;
    public Form1()
    {
        _employees = new();
        InitializeComponent();
        EmployeesListBox.DataSource = _employees;
    }

    private void CreateEmployeeButton_Click(object sender, EventArgs e)
    {
        var employee = new Employee();
        var prompt = new EmployeeCreatorForm(employee);
        prompt.Closing += (_, _) => // No leaking since prompt is closing
        {
            if (!prompt.Completed)
                return;

            _employees.Add(employee);
            Show();
            EmployeesListBox.Refresh();
        };

        Hide();
        prompt.Show();
    }

    private void CreateManagerButton_Click(object sender, EventArgs e)
    {
        var manager = new Manager();
        var prompt = new ManagerCreatorForm(manager);
        prompt.Closing += (_, _) =>
        {
            if (!prompt.Completed)
                return;

            _employees.Add(manager);
            Show();
            EmployeesListBox.Refresh();
        };

        Hide();
        prompt.Show();
    }
}

7 Replies

Mayor McCheese•9mo ago

Doesn't look too unreasonable to me?

DaVinki•9mo ago

That's what I thought but it didn't work. I figured it out after a few hours though, needed to use a BindingSource for DataSource instead of setting it to the list and call ResetBindings(true) on it instead of Refresh on the ListBox

Mayor McCheese•9mo ago

Use wpf 🙂

DaVinki•9mo ago

I agree but it was for a school assignment So it had to be a List<T> and had to be winforms

Mayor McCheese•9mo ago

Why not a bindinglist<t>?

DaVinki•9mo ago

I didn’t know those were a thing, I’ll read about those. Thank you

Accord•9mo 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.

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❔ ✅ WinForms ListBox.DataSource not working