0

这个问题真的很奇怪，并且已经避开了我的调试尝试。仅在 Surface 平板电脑上运行应用程序时才会发生。它不会出现在华硕平板电脑上或在 Visual Studio 中运行时。在飞行模式已打开的特定场景中，会引发我绝对无法捕捉到的 WebException。我什至不完全确定我的代码中的什么导致它发生，因为我的一些日志记录在代码中的某个点之后由于未知原因没有发生。我只能假设它是由 HttpWebRequest 引起的，因为抛出的异常类型似乎来自内部 .NET 组件。这是我能够获得的唯一调试信息。它来自 Windows 事件查看器：

Application: <myappname.exe>
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: System.Net.WebException
Stack:
    at System.Net.ServicePoint.ConnectSocketCallback(System.IAsyncResult)
    at System.Net.LazyAsyncResult.Complete(IntPtr)
    at System.Net.ContextAwareResult.Complete(IntPtr)
    at System.Net.LazyAsyncResult.ProtectedInvokeCallback(System.Object, IntPtr)
    at System.Net.Sockets.Socket.ConnectCallback()
    at System.Net.Sockets.Socket.RegisteredWaitCallback(System.Object, Boolean)
    at System.Threading._ThreadPoolWaitOrTimerCallback.PerformWaitOrTimerCallback(System.Object, Boolean)

我真的希望我有更多的调试信息可以提供，但是我已经尝试了所有我能想到的一切，到处都有大量的 try/catch 块并在大多数调用后记录——其中一些没有被执行。有没有人知道可能导致这种情况的原因？

编辑1：

根据跟踪，异常似乎是在这里的某个地方抛出的。几乎所有东西都包裹在一个 try/catch 块中，所以我看不出 WebException 是如何漏掉的。

byte[] bytes = Encoding.UTF8.GetBytes(requestXml.ToString());
HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url);
request.Method = "POST";
request.ContentType = "text/xml";

try
{
    IAsyncResult requestResult = (IAsyncResult)request.BeginGetRequestStream((rAsyncResult) =>
    {
        using (Stream uploadStream = request.EndGetRequestStream(rAsyncResult))
        {
            try
            {
                uploadStream.Write(bytes, 0, bytes.Length);
                uploadStream.Flush();
            }
            catch (Exception e)
            {
                // Exception handling
            }
            finally
            {
                uploadStream.Dispose();
            }
        }

        IAsyncResult responseResult = (IAsyncResult)request.BeginGetResponse((resAsyncResult) =>
        {
            try
            {
                using (HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(resAsyncResult))
                {
                    try
                    {
                        data = ProcessResponse(XmlReader.Create(response.GetResponseStream()));
                    }
                    catch (Exception e)
                    {
                        // Exception handling
                    }
                    finally
                    {
                        response.Dispose();
                    }
                }
            }
            catch (WebException e)
            {
                // Exception handling
            }

        }, null);
    }, null);
}
catch (Exception e)
{
    // Exception handling
}

编辑2：

我仍然没有找到可接受的解决方案。我目前正在事先检查连接类型，如果代码未连接到 WiFi、移动或以太网，则不允许代码继续运行，但这并没有捕捉到它连接到没有 Internet 连接的网络的情况。WinRT 没有检查互联网连接的解决方案，甚至我使用的方法也不友好（它只是传回一个数字-- http://social.msdn.microsoft.com/Forums/en-US/winappswithcsharp /thread/d8e76732-19d3-47b3-840f-70d87c75ce9f）。

4

3 回答 3

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Did you try handling the Application.UnhandledException?

Add the event handler to the event in the App class constructor:

public App()
{
    // keep the rest of the constructor
    this.UnhandledException += OnUnhandledException;
}

In the event handler you can log the exception and mark is handled to prevent the app from closing / crashing:

void OnUnhandledException(object sender, UnhandledExceptionEventArgs e)
{
    // log e.Exception details for investigation
    e.Handled = true;
}
于 2013-04-05T20:27:26.697 回答
0

就像 Efran Cobisi 所说的 EndGetRequestStream 可能是引发异常的函数。即使有异常， using 语句也会处理对象，因此不需要 try finally 来处理它。但是在任何情况下，您都应该使用异步方法，这将使代码更具可读性并且更容易捕获异常。相当于您的代码将是：

byte[] bytes = Encoding.UTF8.GetBytes(requestXml.ToString());
HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url);
request.Method = "POST";
request.ContentType = "text/xml";

try
{

    using (Stream uploadStream = await request.GetRequestStreamAsync())
    {
        await uploadStream.WriteAsync(bytes, 0, bytes.Length);
        await uploadStream.FlushAsync();
    }

    using (HttpWebResponse response = (HttpWebResponse) await request.GetRequestStreamAsync())
    {
        data = ProcessResponse(XmlReader.Create(response.GetResponseStream()));
    }

}
catch (Exception e)
{
    // Exception
}
于 2013-09-11T19:05:31.520 回答
0

该问题可能是由于您的回调中引发了未处理的异常；回调在与调用初始线程不同的线程中异步执行的可能性很高，request.BeginGetRequestStream这就是为什么您没有在外部 try/catch 块中捕获它的原因。您应该能够通过将回调的全部内容包装在 try/catch 块中来解决此问题，即：

IAsyncResult requestResult = (IAsyncResult)request.BeginGetRequestStream((rAsyncResult) =>
{
    try
    {
        using (Stream uploadStream = request.EndGetRequestStream(rAsyncResult))
        {
            try
            {
                uploadStream.Write(bytes, 0, bytes.Length);
                uploadStream.Flush();
            }
            catch (Exception e)
            {
                // Exception handling
            }
            finally
            {
                uploadStream.Dispose();
            }
        }

        IAsyncResult responseResult = (IAsyncResult)request.BeginGetResponse((resAsyncResult) =>
        {
            try
            {
                using (HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(resAsyncResult))
                {
                    try
                    {
                        data = ProcessResponse(XmlReader.Create(response.GetResponseStream()));
                    }
                    catch (Exception e)
                    {
                        // Exception handling
                    }
                    finally
                    {
                        response.Dispose();
                    }
                }
            }
            catch (WebException e)
            {
                // Exception handling
            }

        }, null);
    }
    catch (Exception ex)
    {
        // Handle the exception as you wish
    }
}, null);
于 2013-09-07T10:08:18.353 回答