[KB]Silverlight搭配WCF，遇到The remote server returned an error: NotFound的錯誤.
最近處理了一個Silverlight搭配WCF的Case，Scenario是這樣地:
User在本機上開發Silverlight搭配WCF的專案，在Visual Studio上執行都很正常，但是佈署到Server上時，就會有問題。
WCF裡使用一個很簡單的函式去回傳一個Hello World字串給Silverlight。 使用者提供了他佈署的網站供我們測試。
1. 當連上網頁時，就看到瀏覽器的左下角報出這樣的錯:
User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; InfoPath.2; MS-RTC LM 8; .NET CLR 3.5.30729; .NET CLR 3.0.30729)
Timestamp: Wed, 21 Oct 2009 03:42:55 UTC
Message: Unhandled Error in Silverlight Application
程式碼: 4004
分類: ManagedRuntimeError
訊息: System.Reflection.TargetInvocationException: An exception occurred during the operation, making the result invalid. Check InnerException for exception details. ---> System.ServiceModel.CommunicationException: The remote server returned an error: NotFound. ---> System.Net.WebException: The remote server returned an error: NotFound. ---> System.Net.WebException: The remote server returned an error: NotFound.
at System.Net.Browser.BrowserHttpWebRequest.InternalEndGetResponse(IAsyncResult asyncResult)
at System.Net.Browser.BrowserHttpWebRequest.<>c__DisplayClass5.<EndGetResponse>b__4(Object sendState)
at System.Net.Browser.AsyncHelper.<>c__DisplayClass2.<BeginOnUI>b__0(Object sendState)
--- End of inner exception stack trace ---
at System.Net.Browser.AsyncHelper.BeginOnUI(SendOrPostCallback beginMethod, Object state)
at System.Net.Browser.BrowserHttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
at System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelAsyncRequest.CompleteGetResponse(IAsyncResult result)
--- End of inner exception stack trace ---
at System.ServiceModel.AsyncResult.End[TAsyncResult](IAsyncResult result)
at System.ServiceModel.Channels.ServiceChannel.SendAsyncResult.End(SendAsyncResult result)
at System.ServiceModel.Channels.ServiceChannel.EndCall(String action, Object[] outs, IAsyncResult result)
at System.ServiceModel.ClientBase`1.ChannelBase`1.EndInvoke(String methodName, Object[] args, IAsyncResult result)
at SilverlightApplication4.CustomerService.SampleServiceClient.SampleServiceClientChannel.EndDoWork(IAsyncResult result)
at SilverlightApplication4.CustomerService.SampleServiceClient.SilverlightApplication4.CustomerService.SampleService.EndDoWork(IAsyncResult result)
at SilverlightApplication4.CustomerService.SampleServiceClient.OnEndDoWork(IAsyncResult result)
at System.ServiceModel.ClientBase`1.OnAsyncCallCompleted(IAsyncResult result)
--- End of inner exception stack trace ---
at System.ComponentModel.AsyncCompletedEventArgs.RaiseExceptionIfNecessary()
at SilverlightApplication4.CustomerService.DoWorkCompletedEventArgs.get_Result()
at SilverlightApplication4.MainPage.client_DoWorkCompleted(Object sender, DoWorkCompletedEventArgs e)
at SilverlightApplication4.CustomerService.SampleServiceClient.OnDoWorkCompleted(Object state)
Line: 54
Char: 13
Code: 0
URI: http://xxxxxxxxxxxxxxxxxx/xxxxxxxxxxxxxx.html
2. 看到System.Net.WebException: The remote server returned an error: NotFound. 的錯誤，心中有了個底，看來，WCF這個服務不乖，沒有好好的運作阿.
3. 去檢視WCF服務的位置, 發現服務未正確執行. 抓到兇手了!
4. 後來找了一下資料，發現原來佈署後要在web.config加上<baseAddressPrefixFilters>的設定，設定佈署站台的基底位址:
<serviceHostingEnvironment aspNetCompatibilityEnabled="true">
<baseAddressPrefixFilters>
<add prefix="http://www.helloworld.com/" />
</baseAddressPrefixFilters>
</serviceHostingEnvironment >
這個tag的說明是這樣:
表示組態項目的集合，這個集合會指定通過篩選條件，而且這些篩選條件提供了一項機制，可在將 Windows Communication Foundation (WCF) 應用程式裝載於網際網路資訊服務 (IIS) 時挑選適當的 IIS 繫結。
簡單地說: 前置詞篩選條件為共用裝載提供者提供一種方式，使其可指定服務所要使用的 URI。
參考資訊:
1. <baseAddressPrefixFilters>
http://msdn.microsoft.com/zh-tw/library/bb924481.aspx
如果您有微軟技術開發的問題，可以到MSDN Forum發問。
如果您有微軟IT管理的問題，可以到TechNet Forum發問喔。
