DataServiceContext.LoadProperty 方法

参考

定义

命名空间:: System.Data.Services.Client

程序集:: System.Data.Services.Client.dll

重要

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从数据服务加载延迟的内容。

重载

LoadProperty(Object, String)	从数据服务加载指定属性的延迟内容。
LoadProperty(Object, String, DataServiceQueryContinuation)	通过使用所提供的查询延续对象，从数据服务加载下一页相关实体。
LoadProperty(Object, String, Uri)	通过使用所提供的下一链接 URI 来加载相关实体页。
LoadProperty<T>(Object, String, DataServiceQueryContinuation<T>)	通过使用所提供的通用查询延续对象，从数据服务加载下一页相关实体。

LoadProperty(Object, String)

从数据服务加载指定属性的延迟内容。

public:
 System::Data::Services::Client::QueryOperationResponse ^ LoadProperty(System::Object ^ entity, System::String ^ propertyName);

public System.Data.Services.Client.QueryOperationResponse LoadProperty (object entity, string propertyName);

member this.LoadProperty : obj * string -> System.Data.Services.Client.QueryOperationResponse

Public Function LoadProperty (entity As Object, propertyName As String) As QueryOperationResponse

参数

entity: Object

包含要加载的属性的实体。

propertyName: String

要加载的指定实体的属性名称。

QueryOperationResponse

对加载操作的响应。

示例

以下示例演示如何显式加载与每个返回的 Customers 实例相关的 Orders 对象。此示例使用DataServiceContext基于 Northwind 数据服务的“添加服务引用”工具生成的，该服务是在完成WCF Data Services 时创建的。

// Create the DataServiceContext using the service URI.
NorthwindEntities context = new NorthwindEntities(svcUri);

try
{
    // Enumerate over the top 10 orders obtained from the context.
    foreach (Order order in context.Orders.Take(10))
    {
        // Explicitly load the customer for each order.
        context.LoadProperty(order, "Customer");

        // Write out customer and order information.
        Console.WriteLine("Customer: {0} - Order ID: {1}",
            order.Customer.CompanyName, order.OrderID);
    }
}
catch (DataServiceQueryException ex)
{
    throw new ApplicationException(
        "An error occurred during query execution.", ex);
}

' Create the DataServiceContext using the service URI.
Dim context = New NorthwindEntities(svcUri)

Try
    ' Enumerate over the top 10 orders obtained from the context.
    For Each order As Order In context.Orders.Take(10)
        ' Explicitly load the customer for each order.
        context.LoadProperty(order, "Customer")

        ' Write out customer and order information.
        Console.WriteLine("Customer: {0} - Order ID: {1}", _
                order.Customer.CompanyName, order.OrderID)
    Next
Catch ex As DataServiceQueryException
    Throw New ApplicationException( _
            "An error occurred during query execution.", ex)
End Try

注解

调用此方法时，将调用网络操作以提取属性值。指定的属性可以是实体的任一属性，包括表示关联或链接的属性。

如果属性是表示关联、链接或延迟的属性，则调用此方法时，会向客户端提供延迟加载相关资源的方式。

如果实体处于未更改或已修改状态，则属性值将加载相关实体，并将这些实体与未更改链接一起标记为“未更改”

如果已加载属性，则调用此方法可让您刷新该属性的值。

适用于

LoadProperty(Object, String, DataServiceQueryContinuation)

通过使用所提供的查询延续对象，从数据服务加载下一页相关实体。

public:
 System::Data::Services::Client::QueryOperationResponse ^ LoadProperty(System::Object ^ entity, System::String ^ propertyName, System::Data::Services::Client::DataServiceQueryContinuation ^ continuation);

public System.Data.Services.Client.QueryOperationResponse LoadProperty (object entity, string propertyName, System.Data.Services.Client.DataServiceQueryContinuation continuation);

member this.LoadProperty : obj * string * System.Data.Services.Client.DataServiceQueryContinuation -> System.Data.Services.Client.QueryOperationResponse

Public Function LoadProperty (entity As Object, propertyName As String, continuation As DataServiceQueryContinuation) As QueryOperationResponse

参数

entity: Object

包含要加载的属性的实体。

propertyName: String

要加载的指定实体的属性名称。

continuation: DataServiceQueryContinuation

DataServiceQueryContinuation<T> 对象，表示要从数据服务加载的下一页相关实体。

QueryOperationResponse

包含下一页相关实体数据的响应。

例外

InvalidOperationException

当 entity 处于 Detached 或 Added 状态时。

注解

当 entity 处于 Unchanged 或 Modified 状态时，在 Unchanged 状态下将相关实体作为对象进行加载，此时链接也处于 Unchanged 状态。

当 entity 处于 Deleted 状态时，在 Unchanged 状态下将相关实体作为对象进行加载，此时链接也处于 Deleted 状态。

适用于

LoadProperty(Object, String, Uri)

通过使用所提供的下一链接 URI 来加载相关实体页。

public:
 System::Data::Services::Client::QueryOperationResponse ^ LoadProperty(System::Object ^ entity, System::String ^ propertyName, Uri ^ nextLinkUri);

public System.Data.Services.Client.QueryOperationResponse LoadProperty (object entity, string propertyName, Uri nextLinkUri);

member this.LoadProperty : obj * string * Uri -> System.Data.Services.Client.QueryOperationResponse

Public Function LoadProperty (entity As Object, propertyName As String, nextLinkUri As Uri) As QueryOperationResponse

参数

entity: Object

包含要加载的属性的实体。

propertyName: String

要加载的指定实体的属性名称。

nextLinkUri: Uri

用于加载下一结果页的 URI。

QueryOperationResponse

包含请求结果的 QueryOperationResponse<T> 实例。

例外

InvalidOperationException

当 entity 处于 Detached 或 Added 状态时。

示例

下面的示例返回每个 Orders 实体的相关 Customers 实体，并使用 do…while 循环从数据服务中加载 Customers 实体页以及使用嵌套的 while 循环从数据服务中加载相关的 Orders 实体的页。 LoadProperty 方法用于加载相关的 Orders 实体页。

// 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);
}

' 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

注解

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。

另请参阅

适用于

LoadProperty<T>(Object, String, DataServiceQueryContinuation<T>)

通过使用所提供的通用查询延续对象，从数据服务加载下一页相关实体。

public:
generic <typename T>
 System::Data::Services::Client::QueryOperationResponse<T> ^ LoadProperty(System::Object ^ entity, System::String ^ propertyName, System::Data::Services::Client::DataServiceQueryContinuation<T> ^ continuation);

public System.Data.Services.Client.QueryOperationResponse<T> LoadProperty<T> (object entity, string propertyName, System.Data.Services.Client.DataServiceQueryContinuation<T> continuation);

member this.LoadProperty : obj * string * System.Data.Services.Client.DataServiceQueryContinuation<'T> -> System.Data.Services.Client.QueryOperationResponse<'T>

Public Function LoadProperty(Of T) (entity As Object, propertyName As String, continuation As DataServiceQueryContinuation(Of T)) As QueryOperationResponse(Of T)

类型参数

T

要加载的集合的元素类型。

参数

entity: Object

包含要加载的属性的实体。

propertyName: String

要加载的指定实体的属性名称。

continuation: DataServiceQueryContinuation<T>

DataServiceQueryContinuation<T> 对象，表示要从数据服务加载的下一页相关实体。

QueryOperationResponse<T>

包含下一页相关实体数据的响应。

例外

InvalidOperationException

当 entity 处于 Detached 或 Added 状态时。

注解

当 entity 处于 Unchanged 或 Modified 状态时，在 Unchanged 状态下将相关实体作为对象进行加载，此时链接也处于 Unchanged 状态。

当 entity 处于 Deleted 状态时，在 Unchanged 状态下将相关实体作为对象进行加载，此时链接也处于 Deleted 状态。

适用于

通过

DataServiceContext.LoadProperty 方法

定义

重载

LoadProperty(Object, String)

参数

返回

示例

注解

适用于

LoadProperty(Object, String, DataServiceQueryContinuation)

参数

返回

例外

注解

适用于

LoadProperty(Object, String, Uri)

参数

返回

例外

示例

注解

另请参阅

适用于

LoadProperty<T>(Object, String, DataServiceQueryContinuation<T>)

类型参数

参数

返回

例外

注解

适用于

其他资源