private void taskTrainneeBindingSource_PositionChanged(object sender, EventArgs e)
        {
            TaskTrainee taskTrainee = (TaskTrainee)TaskTraineeBindingSource.Current;

            if (taskTrainee != null)
            {
                listBoxTaskProject.SelectedValue = taskTrainee.Title;
            }
        }
        /// <summary>
        /// Show TaskTrainee Error
        /// </summary>
        private void showTaskTainneeError()
        {
            foreach (DataGridViewRow row in dataGridViewTaskTranees.Rows)
            {
                TaskTrainee TaskTrainee = (TaskTrainee)row.DataBoundItem;
                if (TaskTrainee != null)
                {
                    if (TaskTrainee.Errors.Count() > 0)
                    {
                        row.DefaultCellStyle.BackColor = Color.Red;

                        foreach (DataGridViewCell cell in row.Cells)
                        {
                            cell.ToolTipText = TaskTrainee.ErrorsMessage();
                            // if (yourCondition) cell.ErrorText = yourErrorText;
                        }
                    }
                }
            }
        }