// to add a customer to the database
public async Task <HttpResponseMessage> PostAsync(Customer customer)
{
List <Customer> customers = await sqlDbHelper.GetCustomers();
// to check if there are no customers with the same card number
//in case of none a new customer will be created
if (customers.Find(a => a.CardNumber == customer.CardNumber) == null)
{
await sqlDbHelper.AddCustomer(customer);
return(Request.CreateResponse(HttpStatusCode.OK, "Created"));
}
// if there are customers already with the same card number, no customers will be created
// and it will return cannot be created string.
else
{
return(Request.CreateResponse(HttpStatusCode.OK, "Cannot be created!"));
}
}