DataServiceContext.LoadProperty 方法

參考

定義

命名空間:: System.Data.Services.Client

組件:: System.Data.Services.Client.dll

重要

部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。

從資料服務載入延遲的內容。

多載

LoadProperty(Object, String)	從資料服務載入指定之屬性的延遲內容。
LoadProperty(Object, String, DataServiceQueryContinuation)	透過使用提供的查詢接續物件，從資料服務載入下一頁相關實體。
LoadProperty(Object, String, Uri)	透過使用提供的下一個連結 URI，載入一頁相關實體。
LoadProperty<T>(Object, String, DataServiceQueryContinuation<T>)	透過使用提供的泛型查詢接續物件，從資料服務載入下一頁相關實體。

LoadProperty(Object, String)

從資料服務載入指定之屬性的延遲內容。

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

參數

entity: Object

包含要載入之屬性的實體。

propertyName: String

要載入的指定之實體的屬性名稱。

傳回

QueryOperationResponse

載入作業的回應。

範例

下列範例示範如何明確地載入與所傳回之每個 Customers 執行個體相關的 Orders 物件。此範例會DataServiceContext根據 Northwind 數據服務使用 Add Service Reference 工具所產生的，當您完成 WCF Data Services 時就會建立此服務參考工具。

// 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

備註

呼叫這個方法會叫用擷取屬性值的網路作業。指定的屬性可能是實體上的任何一個屬性，包括代表關聯或連結的屬性。

如果屬性表示關聯或連結或是擱置的屬性，呼叫這個方法則會提供用戶端一個延遲載入資源的方式。

如果實體處於未變更或已修改狀態，屬性值會載入相關實體，並將這些具有未變更連結的實體標記成未變更。

如果已載入該屬性，則呼叫此方法會讓您重新整理屬性的值。

適用於

LoadProperty(Object, String, DataServiceQueryContinuation)

透過使用提供的查詢接續物件，從資料服務載入下一頁相關實體。

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

參數

entity: Object

包含要載入之屬性的實體。

propertyName: String

要載入的指定之實體的屬性名稱。

continuation: DataServiceQueryContinuation

DataServiceQueryContinuation<T> 物件，表示從資料服務載入的下一頁相關實體。

傳回

QueryOperationResponse

包含下一頁相關實體資料的回應。

例外狀況

InvalidOperationException

當 entity 處於 Detached 或 Added 狀態時。

備註

當 entity 處於 Unchanged 或 Modified 狀態時，相關實體是以 Unchanged 狀態的物件形式載入，而連結也是處於 Unchanged 狀態。

當 entity 處於 Deleted 狀態時，相關實體是以 Unchanged 狀態的物件形式載入，而連結則是處於 Deleted 狀態。

適用於

LoadProperty(Object, String, Uri)

透過使用提供的下一個連結 URI，載入一頁相關實體。

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

參數

entity: Object

包含要載入之屬性的實體。

propertyName: String

要載入的指定之實體的屬性名稱。

nextLinkUri: Uri

用於載入下一個結果頁的 URI。

傳回

QueryOperationResponse

包含要求結果的 QueryOperationResponse<T> 執行個體。

例外狀況

InvalidOperationException

當 entity 處於 Detached 或 Added 狀態時。

範例

本範例會隨每個 Orders 實體傳回相關的 Customers 實體，並使用 do…while 迴圈載入 Customers 實體頁，同時使用巢狀的 while 迴圈從資料服務載入相關 Orders 實體的頁面。 LoadProperty 方法用於載入相關 Orders 實體的頁面。

// 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

備註

當 entity 處於 Unchanged 或 Modified 狀態時，相關實體是以 Unchanged 狀態載入，而且實體之間的連結也是以 Unchanged 狀態建立。

當 entity 處於 Deleted 狀態時，相關實體是以 Unchanged 狀態載入，而實體之間的連結則是以 Deleted 狀態建立。

另請參閱

適用於

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

透過使用提供的泛型查詢接續物件，從資料服務載入下一頁相關實體。

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)

類型參數

T

要載入之集合的元素型別。

參數

entity: Object

包含要載入之屬性的實體。

propertyName: String

要載入的指定之實體的屬性名稱。

continuation: DataServiceQueryContinuation<T>

DataServiceQueryContinuation<T> 物件，表示從資料服務載入的下一頁相關實體。

傳回

QueryOperationResponse<T>

包含下一頁相關實體資料的回應。

例外狀況

InvalidOperationException

當 entity 處於 Detached 或 Added 狀態時。

備註

當 entity 處於 Unchanged 或 Modified 狀態時，相關實體是以 Unchanged 狀態的物件形式載入，而連結也是處於 Unchanged 狀態。

當 entity 處於 Deleted 狀態時，相關實體是以 Unchanged 狀態的物件形式載入，而連結則是處於 Deleted 狀態。

適用於

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DataServiceContext.LoadProperty 方法

定義

多載

LoadProperty(Object, String)

參數

傳回

範例

備註

適用於

LoadProperty(Object, String, DataServiceQueryContinuation)

參數

傳回

例外狀況

備註

適用於

LoadProperty(Object, String, Uri)

參數

傳回

例外狀況

範例

備註

另請參閱

適用於

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

類型參數

參數

傳回

例外狀況

備註

適用於

意見反應

其他資源