进程无法访问文件 <filepath> 因为它正在被另一个进程使用

Question

I'm upload big files dividing its on chunks(small parts) on my ASMX webservice(asmx doesn't support streaming, I not found another way):

bool UploadChunk(byte[] bytes, string path, string md5)
{
      ...
      using (FileStream fs = new FileStream(tempPath, FileMode.Append) )
      {   
            fs.Write( bytes, 0, bytes.Length );
      }
      ...
      return status;
}

but on some files after ~20-50 invokes I catch this error:
The process cannot access the file because it is being used by another process.

I suspect that this related with Windows can't realize the file. Any idea to get rid of this boring error?


the requests executes sequentially and synchronously

client code looks like:

_service.StartUpload(path);

...
do
{
..
bool status = _service.UploadChunk(buf, path, md5);
if(!status)return Status.Failed;
..
}
while(bytesRead > 0);

_service.CheckFile(path, md5);

Answer 1

Each request is handled independently. The process still accessing the file may be the previous request.

In general, you should use file transfer protocols to transfer files. ASMX is not good for that.

And, I presume you have a good reason to not use WCF?

Answer 2

Use WhoLockMe at the moment the error occurs to check who is using the file. You could put the application into debug mode and hold the break point to do this. In all probability it will be your process.

Also try adding a delay after each transfer (and before the next) to see if it helps. Maybe your transfers are too fast and the stream is still in use or being flushed when the next transfer comes in.

Answer 3

use this for creating a file

if you want to append something then add FileMode.Append

var filestreama = new FileStream(name, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite);

Answer 4

Option 1: Get the requirements changed so you don't have to do this using ASMX. WCF supports a streaming model that I'm about to experiment with, but it should be much more effective for what you want.

Option 2: Look into WSE 3.0. I haven't looked at it much, but I think it extends ASMX web services to support things like DIME and MTOM which are designed for transferring files so that may help.

Option 3: Set the system up so that each call writes a piece of the file into a different filename, then write code to rejoin everything at the end.