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HOW TO：設定用戶端要求中的標頭 (WCF Data Services)

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當您使用 WCF Data Services 用戶端程式庫存取支援 Open Data Protocol (OData) 的資料服務時，用戶端程式庫會在傳送至資料服務的要求訊息中自動設定必要的 HTTP 標頭。不過，在某些情況下，用戶端程式庫不知道要設定所需的訊息標頭，例如，當資料服務需要宣告架構的驗證或 Cookie 時。如需詳細資訊，請參閱Securing WCF Data Services。在這些情況下，您必須在以要求訊息中手動設定訊息標頭，然後再傳送出去。本主題中的範例會示範如何處理 SendingRequest 事件，以便將新的標頭加入至要求訊息中，然後再傳送至資料服務。

本主題中的範例使用 Northwind 範例資料服務和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。您也可以使用在 OData 網站上發佈的 Northwind 範例資料服務；此範例資料服務是唯讀的，因此嘗試儲存變更時，會傳回錯誤。OData 網站上的範例資料服務允許匿名驗證。

範例

下列範例會註冊 SendingRequest 事件的處理常式，然後根據資料服務執行查詢。

Gg258441.note(zh-tw,VS.100).gif注意：
當資料服務要求您手動設定每個要求的訊息標頭時，請考慮註冊 SendingRequest 事件的處理常式，方法是，覆寫表示資料服務之實體容器中的 OnContextCreated 部分方法，在此情況下為 NorthwindEntities。 

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

' Register to handle the SendingRequest event.
' Note: If this must be done for every request to the data service, consider
' registering for this event by overriding the OnContextCreated partial method in 
' the entity container, in this case NorthwindEntities. 
AddHandler context.SendingRequest, AddressOf OnSendingRequest

' Define a query for orders with a Freight value greater than 30.
Dim query = From cust In context.Customers _
    Where cust.Country = "Germany" _
    Select cust

Try
    ' Enumerate to execute the query.
    For Each cust As Customer In query
        Console.WriteLine("Name: {0}\nAddress:\n{1}\n{2}, {3}", _
            cust.CompanyName, cust.Address, cust.City, cust.Region)
    Next        
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);

// Register to handle the SendingRequest event.
// Note: If this must be done for every request to the data service, consider
// registering for this event by overriding the OnContextCreated partial method in 
// the entity container, in this case NorthwindEntities. 
context.SendingRequest += new EventHandler<SendingRequestEventArgs>(OnSendingRequest);

// Define a query for orders with a Freight value greater than 30.
var query = from cust in context.Customers
    where cust.Country == "Germany"
    select cust;

try
{
    // Enumerate to execute the query.
    foreach (Customer cust in query)
    {
        Console.WriteLine("Name: {0}\nAddress:\n{1}\n{2}, {3}",
            cust.CompanyName, cust.Address, cust.City, cust.Region);
    }
}
catch (DataServiceQueryException ex)
{
    throw new ApplicationException(
        "An error occurred during query execution.", ex);
}

下列方法會處理 SendingRequest 事件，並將驗證標頭加入至要求中。

Private Shared Sub OnSendingRequest(ByVal sender As Object, ByVal e As SendingRequestEventArgs)
    ' Add an Authorization header that contains an OAuth WRAP access token to the request.
    e.RequestHeaders.Add("Authorization", "WRAP access_token=""123456789""")
End Sub

private static void OnSendingRequest(object sender, SendingRequestEventArgs e)
{
    // Add an Authorization header that contains an OAuth WRAP access token to the request.
    e.RequestHeaders.Add("Authorization", "WRAP access_token=\"123456789\"");
}

另請參閱

概念

保護 WCF Data Services 的安全

其他資源

WCF Data Services 用戶端程式庫