DataServiceContext.AddLink 方法
将指定链接添加到 DataServiceContext 正在跟踪的一组对象。
命名空间： System.Data.Services.Client
程序集： Microsoft.Data.Services.Client（在 Microsoft.Data.Services.Client.dll 中）
语法
声明
Public Sub AddLink ( _
source As Object, _
sourceProperty As String, _
target As Object _
)
用法
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
)
参数
- source
类型：System.Object
新链接的源对象。
- sourceProperty
类型：System.String
源对象上可返回相关对象的导航属性的名称。
- target
类型：System.Object
通过新链接与源对象相关联的对象。
异常
| 异常 | 条件 |
|---|---|
| ArgumentNullException | 当 source、sourceProperty 或 target 为 null 时。 |
| InvalidOperationException | 如果链接已存在。 - 或 - 如果 source 或 target 对象处于 Detached 或 Deleted 状态。 - 或 - 如果 sourceProperty 不是一个集合。 |
注释
通知 DataServiceContext，相关源与目标对象之间存在新链接，且该链接由指定的源属性表示。 DataServiceContext 将此链接添加到新创建的链接集，下次调用 SaveChanges 时，会将该链接集发送到数据服务。 有关详细信息，请参阅更新数据服务（WCF 数据服务）。
目标对象类型必须是 sourceProperty 参数所标识的类型或该类型的子类型。
示例
以下示例演示如何使用 AddLink 和 SetLink 方法来创建用于定义关系的链接。 在此示例中，还显式设置了 Order_Details 对象的导航属性。 此示例使用基于 Northwind 数据服务（在您完成 WCF 数据服务?快速入门时创建）的“添加服务引用”工具所生成的 DataServiceContext。
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);
}