程序是否是线程安全的c# [重复]

Question

我的程序中有一个方法，需要知道它是否是线程安全的。我收到 System.I.O 异常写入这个文件，虽然它不是很一致，它会终止我的程序

方法外提到了文件位置。

private readonly string fileNameAndPath = @"C:\Apps\TestService\log\Test.txt";

public void LogRequestDetails_SendOrderRequestMethod(Message request, SendOrderRequest quoteRequest)
{
    // Create a writer and open the file:
    StreamWriter log;

    if (!File.Exists(fileNameAndPath))
           log = new StreamWriter(fileNameAndPath);
    else
           log = File.AppendText(fileNameAndPath);

    // Write to the file:
    log.WriteLine("=================================");
    log.WriteLine(DateTime.Now);
    log.WriteLine("Price : " + quoteRequest.Price);
    log.WriteLine("QuoteId : " + quoteRequest.QuoteId);
    log.WriteLine("SecurityId : " + quoteRequest.SecurityId);
    log.WriteLine();
    log.WriteLine("Request string : " + request.ToString());
    log.WriteLine("=================================");
    log.WriteLine("\n");

    // Close the stream:
    log.Close();
}

请查看下面的堆栈跟踪

Application: BestInvest.Select.ShareDealingService.exe

Framework Version: v4.0.30319

Description: The process was terminated due to an unhandled exception.

Exception Info: System.IO.IOException

Stack:



Server stack trace: 

   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)

   at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost)

   at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost)

   at System.IO.StreamWriter.CreateFile(String path, Boolean append, Boolean checkHost)

   at System.IO.StreamWriter..ctor(String path, Boolean append, Encoding encoding, Int32 bufferSize, Boolean checkHost)

   at System.IO.StreamWriter..ctor(String path, Boolean append)

   at System.IO.File.AppendText(String path)

   at BestInvest.Direct.Integration.FIXService.ShareDealingEngine.LogRequestDetails_SendOrderRequestMethod(Message request, SendOrderRequest quoteRequest)

   at BestInvest.Direct.Integration.FIXService.ShareDealingEngine.<>c__DisplayClass5.<SendOrder>b__2()

   at System.Runtime.Remoting.Messaging.StackBuilderSink._PrivateProcessMessage(IntPtr md, Object[] args, Object server, Object[]& outArgs)

   at System.Runtime.Remoting.Messaging.StackBuilderSink.AsyncProcessMessage(IMessage msg, IMessageSink replySink)

   at System.Runtime.Remoting.Proxies.RealProxy.EndInvokeHelper(System.Runtime.Remoting.Messaging.Message, Boolean)

   at System.Runtime.Remoting.Proxies.RemotingProxy.Invoke(System.Object, System.Runtime.Remoting.Proxies.MessageData ByRef)

   at System.Action.EndInvoke(System.IAsyncResult)

   at System.Runtime.Remoting.Messaging.AsyncResult.SyncProcessMessage(System.Runtime.Remoting.Messaging.IMessage)

   at System.Runtime.Remoting.Messaging.StackBuilderSink.AsyncProcessMessage(System.Runtime.Remoting.Messaging.IMessage, System.Runtime.Remoting.Messaging.IMessageSink)

   at System.Runtime.Remoting.Proxies.AgileAsyncWorkerItem.ThreadPoolCallBack(System.Object)

   at System.Threading.QueueUserWorkItemCallback.WaitCallback_Context(System.Object)

   at System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)

   at System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)

   at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()

   at System.Threading.ThreadPoolWorkQueue.Dispatch()

   at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()

Answer 1

它不是线程安全的。您可以通过使用锁来保护代码的关键部分免受竞争条件的影响。

private readonly string fileNameAndPath = @"C:\Apps\TestService\log\Test.txt";

private Object thisLock = new Object();

public void LogRequestDetails_SendOrderRequestMethod(Message request, SendOrderRequest quoteRequest)
{
  lock (thisLock)
  {
     // Create a writer and open the file:
     StreamWriter log;

     if (!File.Exists(fileNameAndPath))
       log = new StreamWriter(fileNameAndPath);
     else
       log = File.AppendText(fileNameAndPath);

     // Write to the file:
     log.WriteLine("=================================");
     log.WriteLine(DateTime.Now);
     log.WriteLine("Price : " + quoteRequest.Price);
     log.WriteLine("QuoteId : " + quoteRequest.QuoteId);
     log.WriteLine("SecurityId : " + quoteRequest.SecurityId);
     log.WriteLine();
     log.WriteLine("Request string : " + request.ToString());
     log.WriteLine("=================================");
     log.WriteLine("\n");

     // Close the stream:
     log.Close();
 }
}

更多详情请参阅参考资料： https://msdn.microsoft.com/en-us/library/a8544e2s.aspx

Answer 2

我认为File.Exists 和File.AppendText 是线程安全的，因为它们是静态调用。

但是，对StreamWriter.WriteLine 的实例方法调用不会，所以我认为一个线程可能正在写入文件，而另一个线程可能会在第一个线程完成之前尝试追加，这可能会导致异常。

或者实际上两个线程可以尝试同时使用StreamWriter 写入文件。

System.IOException 上的确切消息是什么？