/// <summary>
        /// validated a input string field and sets the errorprovidor on errors
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private static void ValidateString(object sender, CancelEventArgs e)
        {
            int maxCharCount = 50;

            if (!PackageValidator.IsValidString((TextBox)sender, maxCharCount))
            {
                e.Cancel = true;
            }
        }
        /// <summary>
        /// validates a new package
        /// </summary>
        /// <returns></returns>
        private bool ValidateNewProduct()
        {
            bool validDesc       = PackageValidator.IsValidString(tbxPkgDesc, 50);
            bool validName       = PackageValidator.IsValidString(tbxPkgName, 50);
            bool validEndDate    = PackageValidator.IsValidEndDate(dtpPkgEndDate, dtpPkgStartDate.Value);
            bool validCommission = PackageValidator.IsValidCommission(tbxPkgCommission, tbxPkgPrice);
            bool validPrice      = PackageValidator.IsValidPrice(tbxPkgPrice);

            if (validDesc && validName && validEndDate && validCommission && validPrice)
            {
                return(true);
            }
            else
            {
                return(false);
            }
        }