protected void SearchCustomerB_Click(object sender, EventArgs e)
{
BlUser user = (BlUser)Session["user"];
//get input values
string searchBys = SearchBy.Items[SearchBy.SelectedIndex].Value;
string value = serchedValue.Text;
//get data
DataTable customers = user.CustomersSearch($"(Users.{searchBys}='{value}')");
bool isExist = BindTable(customers, CustomersTable);
ErCustomer.Text = !isExist ? "Not valid search value" : "";//error massage
}