DataServiceContext.LoadProperty 方法 (Object, String, Uri)

项目
04/13/2012

通过使用所提供的下一链接 URI 来加载相关实体页。

用于 Silverlight 的 WCF Data Services 5.0 客户端不支持。

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 Function LoadProperty ( _
    entity As Object, _
    propertyName As String, _
    nextLinkUri As Uri _
) As QueryOperationResponse
用法
Dim instance As DataServiceContext
Dim entity As Object
Dim propertyName As String
Dim nextLinkUri As Uri
Dim returnValue As QueryOperationResponse

returnValue = instance.LoadProperty(entity, _
    propertyName, nextLinkUri)

public QueryOperationResponse LoadProperty(
    Object entity,
    string propertyName,
    Uri nextLinkUri
)

public:
QueryOperationResponse^ LoadProperty(
    Object^ entity, 
    String^ propertyName, 
    Uri^ nextLinkUri
)

member LoadProperty : 
        entity:Object * 
        propertyName:string * 
        nextLinkUri:Uri -> QueryOperationResponse

public function LoadProperty(
    entity : Object, 
    propertyName : String, 
    nextLinkUri : Uri
) : QueryOperationResponse

参数

entity
类型：System.Object
包含要加载的属性的实体。

propertyName
类型：System.String
要加载的指定实体的属性名称。

nextLinkUri
类型：System.Uri
用于加载下一结果页的 URI。

返回值

类型：System.Data.Services.Client.QueryOperationResponse
包含请求结果的 QueryOperationResponse<T> 实例。

异常

异常	条件
InvalidOperationException	当 entity 处于 Detached 或 Added 状态时。

注释

当 entity 处于 Unchanged 或 Modified 状态时，在 Unchanged 状态下加载相关实体，并且也在 Unchanged 状态下创建各实体之间的链接。

当 entity 处于 Deleted 状态时，在 Unchanged 状态下加载相关实体，并在 Deleted 状态下创建各实体之间的链接。

示例

此示例随每个 Customers 实体一起返回相关的 Orders 实体，并使用 do?while 循环从数据服务加载 Customers 实体页以及使用嵌套的 while 循环从数据服务加载相关的 Orders 实体页。 LoadProperty 方法用于加载相关的 Orders 实体页。

' Create the DataServiceContext using the service URI.
Dim context = New NorthwindEntities(svcUri)
Dim nextLink As DataServiceQueryContinuation(Of Customer) = Nothing
Dim pageCount = 0
Dim innerPageCount = 0

Try
    ' Execute the query for all customers and related orders,
    ' and get the response object.
    Dim response = _
    CType(context.Customers.AddQueryOption("$expand", "Orders") _
            .Execute(), QueryOperationResponse(Of Customer))

    ' With a paged response from the service, use a do...while loop 
    ' to enumerate the results before getting the next link.
    Do
        ' Write the page number.
        Console.WriteLine("Customers Page {0}:", ++pageCount)

        ' If nextLink is not null, then there is a new page to load.
        If nextLink IsNot Nothing Then
            ' Load the new page from the next link URI.
            response = CType(context.Execute(Of Customer)(nextLink),  _
                    QueryOperationResponse(Of Customer))
        End If

        ' Enumerate the customers in the response.
        For Each c As Customer In response
            Console.WriteLine(vbTab & "Customer Name: {0}", c.CompanyName)
            Console.WriteLine(vbTab & "Orders Page {0}:", innerPageCount + 1)

            ' Get the next link for the collection of related Orders.
            Dim nextOrdersLink As DataServiceQueryContinuation(Of Order) = _
            response.GetContinuation(c.Orders)

            While nextOrdersLink IsNot Nothing
                For Each o As Order In c.Orders
                    ' Print out the orders.
                    Console.WriteLine(vbTab & vbTab & "OrderID: {0} - Freight: ${1}", _
                            o.OrderID, o.Freight)
                Next
                ' Load the next page of Orders.
                Dim ordersResponse = _
                context.LoadProperty(c, "Orders", nextOrdersLink)
                nextOrdersLink = ordersResponse.GetContinuation()
            End While
        Next
        ' Get the next link, and continue while there is a next link.
        nextLink = response.GetContinuation()
    Loop While nextLink IsNot Nothing
Catch ex As DataServiceQueryException
    Throw New ApplicationException( _
            "An error occurred during query execution.", ex)
End Try

// Create the DataServiceContext using the service URI.
NorthwindEntities context = new NorthwindEntities(svcUri);
DataServiceQueryContinuation<Customer> nextLink = null;
int pageCount = 0;
int innerPageCount = 0;

try
{
    // Execute the query for all customers and related orders,
    // and get the response object.
    var response =
        context.Customers.AddQueryOption("$expand", "Orders")
        .Execute() as QueryOperationResponse<Customer>;

    // With a paged response from the service, use a do...while loop 
    // to enumerate the results before getting the next link.
    do
    {
        // Write the page number.
        Console.WriteLine("Customers Page {0}:", ++pageCount);

        // If nextLink is not null, then there is a new page to load.
        if (nextLink != null)
        {
            // Load the new page from the next link URI.
            response = context.Execute<Customer>(nextLink)
                as QueryOperationResponse<Customer>;
        }

        // Enumerate the customers in the response.
        foreach (Customer c in response)
        {
            Console.WriteLine("\tCustomer Name: {0}", c.CompanyName);
            Console.WriteLine("\tOrders Page {0}:", ++innerPageCount);
            // Get the next link for the collection of related Orders.
            DataServiceQueryContinuation<Order> nextOrdersLink = 
                response.GetContinuation(c.Orders);

            while (nextOrdersLink != null)
            {
                foreach (Order o in c.Orders)
                {
                    // Print out the orders.
                    Console.WriteLine("\t\tOrderID: {0} - Freight: ${1}",
                        o.OrderID, o.Freight);
                }

                // Load the next page of Orders.
                var ordersResponse = context.LoadProperty(c, "Orders", nextOrdersLink);
                nextOrdersLink = ordersResponse.GetContinuation();
            }
        }
    }

    // Get the next link, and continue while there is a next link.
    while ((nextLink = response.GetContinuation()) != null);
}
catch (DataServiceQueryException ex)
{
    throw new ApplicationException(
        "An error occurred during query execution.", ex);
}