private void Import_Click(object sender, EventArgs e)
        {
            bool continueImport = true;
            if (!User.UserCheck()) {
                Password password = new Password {
                    IsLogin = false
                };
                continueImport = (password.ShowDialog() == System.Windows.Forms.DialogResult.OK);
            }

            if (continueImport) {
                if (OpenFile.ShowDialog() != DialogResult.Cancel) {
                    ImportKeyFile.Import(OpenFile.FileName, User.GetPassword());
                    LoadProducts();
                }
            }
        }
        private static bool Login()
        {
            bool continueLogin = true;
            if (!User.UserCheck()) {
                Password password = new Password {
                    IsLogin = false
                };
                continueLogin = (password.ShowDialog() == System.Windows.Forms.DialogResult.OK);
            }

            if (continueLogin) {
                Password password = new Password {
                    IsLogin = true
                };
                if (password.ShowDialog() == System.Windows.Forms.DialogResult.OK) {
                    return true;
                }
            }
            return false;
        }