c# 7 new features

Error de actualización usando(ling a sql)

Question

Tengo dos tablas, vinculadas por clave externa CarrierID:

Carrier[CarrierID,CarrierName]
CarrierID = 1, CarrierName = DHL
CarrierID = 2, CarrierName = Fedex
...
Vendor[VendorID, VendorName, CarrierID]
VendorID = 1, VendorName =D-link , CarrierID=1
VendorID = 2, VendorName = Netbes , CarrierID= 2

Cuando intento actualizar el nombre del operador en la vista de proveedor. Recibo este error "ForeignKeyReferenceAlreadyHasValueException"

Tengo clase llamada editvendor

public static void editvendor(Vendor vendor)
{
using (MyinvoiceDataDataContext connv = new MyinvoiceDataDataContext())
{
Vendor editven = (from s in connv.Vendors
where s.VendorID == vendor.VendorID
select s).FirstOrDefault();
editven.VendorAddress = editven.VendorAddress;
editven.VendorBalance = editven.VendorBalance;
editven.VendorContactName = editven.VendorContactName;
editven.VendorEmail = editven.VendorEmail;
editven.VendorFax = editven.VendorFax;
editven.VendorName = editven.VendorName;
editven.VendorPaymentTerms = editven.VendorPaymentTerms;
editven.VendorPhone = editven.VendorPhone;
editven.VendorRemark = editven.VendorRemark;
editven.VendorTax = editven.VendorTax;
editven.VendorWebsite = editven.VendorWebsite;
editven.CarrierID = editven.Carrier.CarrierID;
connv.SubmitChanges();
}
}
#endregion

En el formulario de Windows (editar el formulario del proveedor), uso esto:

 private void Window_Loaded(object sender, RoutedEventArgs e)
{
MyinvoiceDataDataContext contecta = new MyinvoiceDataDataContext();
var tb = from s in contecta.Carriers
select new { s.CarrierID, s.CarrierName };
comVendorCarrier.ItemsSource = tb;
comVendorCarrier.DisplayMemberPath = "CarrierName";
comVendorCarrier.SelectedValuePath = "CarrierID";
ViewVendor vendview = new ViewVendor();
txtVendorName.Text = vendor.VendorName.Trim();
txtVendorBalance.Text = vendor.VendorBalance.Trim();
txtVendorContactName.Text = vendor.VendorContactName.Trim();
txtVendorPhone.Text = vendor.VendorPhone.Trim();
txtVendorFax.Text = vendor.VendorTax.Trim();
txtVendorEmail.Text = vendor.VendorEmail.Trim();
txtVendorWebsite.Text = vendor.VendorWebsite.Trim();
txtVendorRemarks.Text = vendor.VendorRemark.Trim();
txtVendorAddress.Text = vendor.VendorAddress.Trim();
txtVendorTax.Text = vendor.VendorTax.Trim();
comVendorCarrier.Text = vendor.Carrier.CarrierName.Trim();
ComVendorPaymentTerms.Text = vendor.VendorPaymentTerms.Trim();
}

Este código lo uso para guardar el proveedor editado

 private void EditVendorSavebtn_Click_1(object sender, RoutedEventArgs e)
{
int SelectedCarrierId = int.Parse(comVendorCarrier.SelectedValue.ToString());
if (txtVendorName.Text.Trim() == "")
MessageBox.Show("Please fill vendor''s Name");
if (txtVendorBalance.Text.Trim() == "")
MessageBox.Show("Please fill vendor''s balance");
if (txtVendorContactName.Text.Trim() == "")
MessageBox.Show("Please fill vendor''s contact name");
if (txtVendorPhone.Text.Trim() == "")
MessageBox.Show("Please fill vendor''s phone number");
if (txtVendorFax.Text.Trim() == "")
MessageBox.Show("Please fill vendor''s fax number");
if (txtVendorEmail.Text.Trim() == "")
MessageBox.Show("Please fill vendor''s E-maill");
if (txtVendorWebsite.Text.Trim() == "")
MessageBox.Show("Please fill vendor''s Website");
if (txtVendorAddress.Text.Trim() == "")
MessageBox.Show("Please fill vendor''s address");
else
{
vendor.VendorName = txtVendorName.Text.Trim();
vendor.VendorBalance = txtVendorBalance.Text.Trim();
vendor.VendorContactName = txtVendorContactName.Text.Trim();
vendor.VendorPhone = txtVendorPhone.Text.Trim();
vendor.VendorFax = txtVendorFax.Text.Trim();
vendor.VendorEmail = txtVendorEmail.Text.Trim();
vendor.VendorWebsite = txtVendorWebsite.Text.Trim();
vendor.VendorRemark = txtVendorRemarks.Text.Trim();
vendor.VendorAddress = txtVendorAddress.Text.Trim();
vendor.VendorPaymentTerms = ComVendorPaymentTerms.Text;
vendor.CarrierID = SelectedCarrierId;
vendor.VendorTax = txtVendorFax.Text.Trim();
vendorinfo.editvendor(vendor);
MessageBox.Show(vendor.VendorName + " succesfully edited.");
Window_Loaded(null, null);
}

Answer 1

Espero que sea esta combinación:

// somewhere
comVendorCarrier.Text = vendor.Carrier.CarrierName.Trim();
...
// somewhere else
vendor.CarrierID = SelectedCarrierId;

Uno está utilizando el enfoque orientado a objetos, uno está utilizando el enfoque basado en id. Sin embargo, si ambos están cargados y son incompatibles , hay problemas. Me pregunto si deberías usar:

vendor.Carrier = null;
vendor.CarrierID = SelectedCarrierId;

entonces hay exactamente una definición de qué operador usar.

Alternativamente, maneje el operador por separado, por ejemplo, en lugar de:

comVendorCarrier.Text = vendor.Carrier.CarrierName.Trim();

utilizar:

var carrier = context.Carriers.Single(x => x.Id = vendor.CarrierId);
comVendorCarrier.Text = carrier.CarrierName.Trim();

que luego nunca carga el vendor.Carrier . vendor.Carrier como un objeto.