DataServiceContext.SetLink(Object, String, Object) 方法

public:
 void SetLink(System::Object ^ source, System::String ^ sourceProperty, System::Object ^ target);

public void SetLink(object source, string sourceProperty, object target);

member this.SetLink : obj * string * obj -> unit

Public Sub SetLink (source As Object, sourceProperty As String, target As Object)

参数

例外

示例

以下示例演示如何使用 AddLink 和 SetLink 方法创建定义关系的链接。 在此示例中，还会显式设置对象上的 Order_Details 导航属性。

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);
}

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)

注解

在状态中创建 Added 一个新链接。 在下一次调用DataServiceContext时，会将SaveChanges此新链接添加到要发送到数据服务的新链接集。

如果目标参数为 null，则应删除或删除 sourceProperty 表示的链接（链接已移动到 Deleted 状态）。

链接是单向关系。 如果存在指示双向关联的后指针，则应再次调用此方法以通知 DataServiceContext 第二个链接

此方法仅支持将链接添加到具有多重性 = 1 的关系（源属性是对象引用）。 例如，如果类与属性的另一个类Person相关，则此调用可用于关联。PersonFriendPersonPerson 如果 sourceProperty 表示的具有多个基数关系，则此方法将引发异常。