VB.NET ObjectContext.DeleteObject方法代碼示例

Dim deletedProduct As Object

' Define the key of the product to delete. 
Dim productKey As New EntityKey("AdventureWorksEntities.Products", "ProductID", productId)

Using context As New AdventureWorksEntities()
    ' Get the object to delete with the specified key. 
    If context.TryGetObjectByKey(productKey, deletedProduct) Then
        Try
            ' Delete the object with the specified key 
            ' and save changes to delete the row from the data source. 
            context.DeleteObject(deletedProduct)
            context.SaveChanges()
        Catch ex As OptimisticConcurrencyException
            Throw New InvalidOperationException(String.Format("The product with an ID of '{0}' could not be deleted." & _
                                                              "Make sure that any related objects are already deleted.", _
                                                              productKey.EntityKeyValues(0).Value), ex)
        End Try
    Else
        Throw New InvalidOperationException(String.Format("The product with an ID of '{0}' could not be found." & _
                                                          "Make sure that Product exists.", productKey.EntityKeyValues(0).Value))
    End If
End Using

' Specify the order to update. 
Dim orderId As Integer = 43680

Using context As New AdventureWorksEntities()
    Try
        Dim order = (From o In context.SalesOrderHeaders
            Where o.SalesOrderID = orderId
            Select o).First()

        ' Change the status and ship date of an existing order. 
        order.Status = 1
        order.ShipDate = DateTime.Today

        ' You do not have to call the Load method to load the details for the order, 
        ' because lazy loading is set to true 
        ' by the constructor of the AdventureWorksEntities object. 
        ' With lazy loading set to true the related objects are loaded when 
        ' you access the navigation property. In this case SalesOrderDetails. 

        ' Delete the first item in the order. 
        context.DeleteObject(order.SalesOrderDetails.First())

        ' Create a new SalesOrderDetail object. 
        ' You can use the static CreateObjectName method (the Entity Framework 
        ' adds this method to the generated entity types) instead of the new operator: 
        ' SalesOrderDetail.CreateSalesOrderDetail(1, 0, 2, 750, 1, (decimal)2171.2942, 0, 0, 
        ' Guid.NewGuid(), DateTime.Today)) 
        Dim detail = New SalesOrderDetail With
        {
            .SalesOrderID = 0,
            .SalesOrderDetailID = 0,
            .OrderQty = 2,
            .ProductID = 750,
            .SpecialOfferID = 1,
            .UnitPrice = CDec(2171.2942),
            .UnitPriceDiscount = 0,
            .LineTotal = 0,
            .rowguid = Guid.NewGuid(),
            .ModifiedDate = DateTime.Now
        }
        order.SalesOrderDetails.Add(detail)

        ' Save changes in the object context to the database. 
        Dim changes As Integer = context.SaveChanges()

        Console.WriteLine(changes.ToString() + " changes saved!")
        Console.WriteLine("Updated item for order: {0}", order.SalesOrderID.ToString())

        For Each item As SalesOrderDetail In order.SalesOrderDetails
            Console.WriteLine("Item ID: {0}", item.SalesOrderDetailID.ToString())
            Console.WriteLine("Product: {0}", item.ProductID.ToString())
            Console.WriteLine("Quantity: {0}", item.OrderQty.ToString())
        Next
    Catch ex As UpdateException
        Console.WriteLine(ex.ToString())
    End Try
End Using