public string AddCustomer(string customer)
 {
     DataAccess da = new DataAccess();
     //Check om Customer allerede findes
     if (!da.customerExist(customer))
     {
         if (da.AddCustomer(customer))
         {
             return "Customer added";
         }
         else
         {
             return "Error, while adding customer";
         }
     }
     else
     {
         return "Customer already exist";
     }
 }