The wrong way to display a WinForms modal dialog

winforms_display_model_bad.cs

private void btnShowUserDialog_Click(object sender, EventArgs e)  
{
    var form = new SelectUserForm();  // Wrap in using block

    form.SelectedUsers = SelectedUsers;

    // Don't use a custom event.
    // Instead get the selected users after the ShowDialog() method returns.
    form.OkClick += SelectUserForm_OnOkClick;

    form.ShowDialog(this);

    // Use the built-in DialogResult property instead of
    // creating a custom property.
    if (form.Success)
    {
        lblUsers.Text = SelectedUsers.Values.ToDelimitedString(", ");
        lblUsers.Tag = SelectedUsers.Keys.ToDelimitedString(",");
    }

    // Missing call to form.Dispose()
}

private void SelectUserForm_OnOkClick(object sender, EventArgs e)  
{
    // Creating a custom event to process results is unnecessary
    SelectedUsers = ((SelectUserForm)sender).SelectedUsers;
}