DataServiceContext.AddLink 方法
將指定的連結加入 DataServiceContext 正在追蹤的物件集。
命名空間： System.Data.Services.Client
組件： Microsoft.Data.Services.Client (在 Microsoft.Data.Services.Client.dll 中)
語法
'宣告
Public Sub AddLink ( _
source As Object, _
sourceProperty As String, _
target As Object _
)
'用途
Dim instance As DataServiceContext
Dim source As Object
Dim sourceProperty As String
Dim target As Object
instance.AddLink(source, sourceProperty, _
target)
public void AddLink(
Object source,
string sourceProperty,
Object target
)
public:
void AddLink(
Object^ source,
String^ sourceProperty,
Object^ target
)
member AddLink :
source:Object *
sourceProperty:string *
target:Object -> unit
public function AddLink(
source : Object,
sourceProperty : String,
target : Object
)
參數
- source
型別：System.Object
新連結的來源物件。
- sourceProperty
型別：System.String
來源物件上傳回相關物件的導覽屬性名稱。
- target
型別：System.Object
透過新連結與來源物件相關的物件。
例外狀況
| 例外狀況 | 條件 |
|---|---|
| ArgumentNullException | 當 source、sourceProperty 或 target 為 null 時。 |
| InvalidOperationException | 如果連結已存在。 -或- 如果 source 或 target 物件處於 Detached 或 Deleted 狀態。 -或- 如果 sourceProperty 不是集合。 |
備註
通知 DataServiceContext 相關來源與目標物件之間有新連結，而且連結是以指定的來源屬性表示。 DataServiceContext 會將這個連結加入新建立的連結集，而在對 SaveChanges 的下一個呼叫時便會將該連結集傳送至資料服務。 如需詳細資訊，請參閱更新資料服務 (WCF Data Services)。
目標物件必須是 sourceProperty 參數所識別的型別，或是該型別的子型別。
範例
下列範例示範如何使用 AddLink 和 SetLink 方法來建立定義關聯性的連結。 此範例中也會明確設定 Order_Details 物件的導覽屬性。 此範例使用「加入服務參考」工具所產生的 DataServiceContext，並根據完成 WCF Data Services 快速入門時所建立的 Northwind 資料服務。
Dim productId = 25
Dim customerId = "ALFKI"
Dim newItem As Order_Detail = Nothing
' Create the DataServiceContext using the service URI.
Dim context = New NorthwindEntities(svcUri)
Try
' Get the specific product.
Dim selectedProduct = (From product In context.Products _
Where product.ProductID = productId _
Select product).Single()
' Get the specific customer.
Dim cust = (From customer In context.Customers.Expand("Orders") _
Where customer.CustomerID = customerId _
Select customer).Single()
' Get the first order.
Dim order = cust.Orders.FirstOrDefault()
' Create a new order detail for the specific product.
newItem = Order_Detail.CreateOrder_Detail( _
order.OrderID, selectedProduct.ProductID, 10, 5, 0)
' Add the new order detail to the context.
context.AddToOrder_Details(newItem)
' Add links for the one-to-many relationships.
context.AddLink(order, "Order_Details", newItem)
context.AddLink(selectedProduct, "Order_Details", newItem)
' Add the new order detail to the collection, and
' set the reference to the product.
order.Order_Details.Add(newItem)
newItem.Product = selectedProduct
' Send the insert to the data service.
Dim response As DataServiceResponse = context.SaveChanges()
' Enumerate the returned responses.
For Each change As ChangeOperationResponse In response
' Get the descriptor for the entity.
Dim descriptor = TryCast(change.Descriptor, EntityDescriptor)
If Not descriptor Is Nothing Then
Dim addedProduct = TryCast(descriptor.Entity, Product)
If Not addedProduct Is Nothing Then
Console.WriteLine("New product added with ID {0}.", _
addedProduct.ProductID)
End If
End If
Next
Catch ex As DataServiceQueryException
Throw New ApplicationException( _
"An error occurred when saving changes.", ex)
' Handle any errors that may occur during insert, such as
' a constraint violation.
Catch ex As DataServiceRequestException
Throw New ApplicationException( _
"An error occurred when saving changes.", ex)
int productId = 25;
string customerId = "ALFKI";
Order_Detail newItem = null;
// Create the DataServiceContext using the service URI.
NorthwindEntities context = new NorthwindEntities(svcUri);
try
{
// Get the specific product.
var selectedProduct = (from product in context.Products
where product.ProductID == productId
select product).Single();
// Get the specific customer.
var cust = (from customer in context.Customers.Expand("Orders")
where customer.CustomerID == customerId
select customer).Single();
// Get the first order.
Order order = cust.Orders.FirstOrDefault();
// Create a new order detail for the specific product.
newItem = Order_Detail.CreateOrder_Detail(
order.OrderID, selectedProduct.ProductID, 10, 5, 0);
// Add the new order detail to the context.
context.AddToOrder_Details(newItem);
// Add links for the one-to-many relationships.
context.AddLink(order, "Order_Details", newItem);
context.AddLink(selectedProduct, "Order_Details", newItem);
// Add the new order detail to the collection, and
// set the reference to the product.
order.Order_Details.Add(newItem);
newItem.Product = selectedProduct;
// Send the changes to the data service.
DataServiceResponse response = context.SaveChanges();
// Enumerate the returned responses.
foreach (ChangeOperationResponse change in response)
{
// Get the descriptor for the entity.
EntityDescriptor descriptor = change.Descriptor as EntityDescriptor;
if (descriptor != null)
{
if (descriptor.Entity.GetType() == typeof(Order_Detail))
{
Order_Detail addedItem = descriptor.Entity as Order_Detail;
if (addedItem != null)
{
Console.WriteLine("New {0} item added to order {1}.",
addedItem.Product.ProductName, addedItem.OrderID.ToString());
}
}
}
}
}
catch (DataServiceQueryException ex)
{
throw new ApplicationException(
"An error occurred when saving changes.", ex);
}
// Handle any errors that may occur during insert, such as
// a constraint violation.
catch (DataServiceRequestException ex)
{
throw new ApplicationException(
"An error occurred when saving changes.", ex);
}