Geek Answers Handbook

Try to catch async, expect https exceptions

I have what seems like a really strange situation. I have some async / await code that uses RestSharp to retrieve some data from several leisure APIs (the same API hosted on different URLs) that returns the look of a directory service.

Now the problem: one of the APIs returned by the specified directory service is somehow "private" and initiating an SSL connection to it fails. Fiddler captures the following response:

HTTP/1.1 200 Connection Established
FiddlerGateway: Direct
StartTime: 19:13:11.117
Connection: close

fiddler.network.https> HTTPS handshake to foo.bar.com failed. System.IO.IOException The handshake failed due to an unexpected packet format.

Ideally, I would like to skip getting data from this API in case this happens, and just move on. However, the attempt / catch does not help! A NullReferenceException has been thrown, but even a common try / catch cannot catch it.

The code is pretty simple:

try
{
   await GetDataAsync(url);
}
catch 
{
   // never gets called
}

and

private async Task<List<Data>> GetDataAsync(string url)
{
   var request = new RestRequest("/foo");
   var restClient = new RestClient(url);

   var response = await restClient.ExecuteTaskAsync<List<Data>>(request); // <-- this throws 
   return response.Data;
}

, WPF, , catch .

?

l.e.: ,

Unhandled Exception: System.NullReferenceException: Object reference not set to
an instance of an object.
at RestSharp.RestClient.<>c__DisplayClass15`1.<ExecuteTaskAsync>b__12(IRestResponse`1 response, RestRequestAsyncHandle _)
at RestSharp.RestClient.DeserializeResponse[T](IRestRequest request, Action`2 callback, IRestResponse response, RestRequestAsyncHandle asyncHandle)
at RestSharp.RestClient.<>c__DisplayClassa`1.<ExecuteAsync>b__9(IRestResponse response, RestRequestAsyncHandle asyncHandle)
at RestSharp.RestClient.ProcessResponse(IRestRequest request, HttpResponse httpResponse, RestRequestAsyncHandle asyncHandle, Action`2 callback)
at RestSharp.RestClient.<>c__DisplayClass3.<ExecuteAsync>b__0(HttpResponse r)
at RestSharp.Http.ExecuteCallback(HttpResponse response, Action`1 callback)
at RestSharp.Http.ResponseCallback(IAsyncResult result, Action`1 callback)
at RestSharp.Http.<>c__DisplayClass3.<GetStyleMethodInternalAsync>b__1(IAsyncResult result)
at System.Net.LazyAsyncResult.Complete(IntPtr userToken)
at System.Net.ContextAwareResult.CompleteCallback(Object state)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Net.ContextAwareResult.Complete(IntPtr userToken)
at System.Net.LazyAsyncResult.ProtectedInvokeCallback(Object result, IntPtr userToken)
at System.Net.HttpWebRequest.SetResponse(Exception E)
at System.Net.HttpWebRequest.CheckWriteSideResponseProcessing()
at System.Net.ConnectStream.ProcessWriteCallDone(ConnectionReturnResult returnResult)
at System.Net.HttpWebRequest.WriteCallDone(ConnectStream stream, ConnectionReturnResult returnResult)
at System.Net.ConnectStream.CallDone(ConnectionReturnResult returnResult)
at System.Net.ConnectStream.IOError(Exception exception, Boolean willThrow)
at System.Net.ConnectStream.HandleWriteHeadersException(Exception e, WebExceptionStatus error)
at System.Net.ConnectStream.WriteHeadersCallback(IAsyncResult ar)
at System.Net.LazyAsyncResult.Complete(IntPtr userToken)
at System.Net.LazyAsyncResult.ProtectedInvokeCallback(Object result, IntPtr userToken)
at System.Net.TlsStream.ResumeIOWorker(Object result)
at System.Net.TlsStream.WakeupPendingIO(IAsyncResult ar)
at System.Net.LazyAsyncResult.Complete(IntPtr userToken)
at System.Net.LazyAsyncResult.ProtectedInvokeCallback(Object result, IntPtr userToken)
at System.Net.Security.SslState.FinishHandshake(Exception e, AsyncProtocolRequest asyncRequest)
at System.Net.Security.SslState.PartialFrameCallback(AsyncProtocolRequest asyncRequest)
at System.Net.AsyncProtocolRequest.CompleteRequest(Int32 result)
at System.Net.FixedSizeReader.CheckCompletionBeforeNextRead(Int32 bytes)
at System.Net.FixedSizeReader.ReadCallback(IAsyncResult transportResult)
at System.Net.LazyAsyncResult.Complete(IntPtr userToken)
at System.Net.ContextAwareResult.CompleteCallback(Object state)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Net.ContextAwareResult.Complete(IntPtr userToken)
at System.Net.LazyAsyncResult.ProtectedInvokeCallback(Object result, IntPtr userToken)
at System.Net.Sockets.BaseOverlappedAsyncResult.CompletionPortCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* nativeOverlapped)
at System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32errorCode, UInt32 numBytes, NativeOverlapped* pOVERLAP)
+4
2

, RestSharp. , - RestSharp.

+2

Try Catch Async (GetDataAsync) , , , , : :

,

( )

http://www.interact-sw.co.uk/iangblog/2010/11/01/csharp5-async-exceptions

-1

More articles:


All Articles