當您在 WCF Data Services 中加入新的實體時，並不會自動定義新實體與相關實體之間的任何關聯性。 您可以建立和變更實體執行個體之間的關聯性，而且可以讓用戶端程式庫在資料服務中反映這些變更。 如需詳細資訊，請參閱更新資料服務 (WCF Data Services)。
本主題的範例使用 Northwind 範例資料服務，以及自動產生的用戶端資料服務類別。 此服務和用戶端資料類別會在您完成 WCF Data Services 快速入門時建立。
範例
下列範例會建立一個新的物件執行個體，然後呼叫 DataServiceContext 的 AddRelatedObject 方法，在內容中建立項目與相關訂單的連結。 呼叫 SaveChanges 方法時，會將 HTTP POST 訊息傳送至資料服務。
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 item with a link to the related order.
context.AddRelatedObject(order, "Order_Details", newItem)
' Add the new order detail to the collection, and
' set the reference to the product.
order.Order_Details.Add(newItem)
newItem.Order = order
newItem.Product = selectedProduct
' Send the changes 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
If TypeOf descriptor.Entity Is Order_Detail Then
Dim addedItem = TryCast(descriptor.Entity, Order_Detail)
If Not addedItem Is Nothing Then
Console.WriteLine("New {0} item added to order {1}.", _
addedItem.Product.ProductName, addedItem.OrderID.ToString())
End If
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 item with a link to the related order.
context.AddRelatedObject(order, "Order_Details", newItem);
// Add the new order detail to the collection, and
// set the reference to the product.
order.Order_Details.Add(newItem);
newItem.Order = order;
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);
}
下列範例示範如何使用 AddObject 方法將 Order_Details 物件加入至相關的 Orders 物件 (包含特定 Products 物件的參考)。 AddLink 和 SetLink 方法可定義關聯性。 此範例中也會明確設定 Order_Details 物件的導覽屬性。
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);
}
請參閱
工作
HOW TO：新增、修改及刪除實體 (WCF Data Services)