You might be able to do that with an overlapped IOCTL using NtFsControlFile.
But I think that the driver can choose to exhibit synchronous behavior even
for overlapped requests.

Hi Dave,

Yes, you are correct. We have asynchronous version FileStream related
operation, e.g. BeginRead/BeginWrite. But we did NOT have such a BeginFlush
method.
So to make the Flush method(a synchronous method) to be asynchronous, we
have to do the flush in another thread.
The link I posted has a few method to run certain method on another thread.
Here I post the code snippet using asynchronous Delegate to implement an
asynchronous method call)

   class Program
   {
       public delegate bool FlushDelegate();
       public static FileStream fs = null;
       public static bool FlushDelegateFunc()
       {
           Console.WriteLine("Flush ThreadID: " +
Thread.CurrentThread.ManagedThreadId);
           fs.Flush();
           return true;
       }
       static void Main(string[] args)
       {
           fs = new FileStream(@"test.txt", FileMode.OpenOrCreate);
           fs.Write(new byte[] { 1, 2 }, 0, 2);
           FlushDelegate fDelegate = new FlushDelegate(FlushDelegateFunc);
           IAsyncResult ar = fDelegate.BeginInvoke(null, null); //This
call will return immediately.
           Console.WriteLine("Main ThreadID: " +
Thread.CurrentThread.ManagedThreadId);
           Console.WriteLine("Wait for flush thread return");
           fDelegate.EndInvoke(ar);
       }
   }

NOTE: Because here actually is a multiple threading programming, so we need
to guarantee that the object accessed from the two
threads(Main,FlushDelegateFunc) are thread safe.
From MSDN the public static version of FileStream is  thread safe.

If I misunderstood, or  you have any other concern, please feel free to let
me know.

Best regards,

Peter Huang

Microsoft Online Community Support
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