使用输入流创建文件会导致访问被拒绝问题

Question

我已经创建了一个WCF方法，它将根据传递的输入流创建一个文件。第一次调用该方法时，它会创建没有任何问题的文件。下次时间调用会导致路径被拒绝访问...任何帮助解决问题。

wcf函数如下

  public void UploadFile1(RemoteFileInfo1 request)
        {
            FileStream targetStream = null;
            Stream sourceStream = request.FileByteStream;

            request.FilePath = "\\" + request.FilePath;


            if (!Directory.Exists(request.FilePath))
            {

                Directory.CreateDirectory(request.FilePath);

            }
            string filePath = Path.Combine(request.FilePath, request.FileName);

            using (targetStream = new FileStream(filePath, FileMode.Create, FileAccess.Write, FileShare.None))
            {
                //read from the input stream in 6K chunks
                //and save to output stream
                const int bufferLen = 65000;
                byte[] buffer = new byte[bufferLen];
                int count = 0;
                while ((count = sourceStream.Read(buffer, 0, bufferLen)) > 0)
                {
                    targetStream.Write(buffer, 0, count);
                }
                targetStream.Close();
                sourceStream.Close();
            }        

        }

request.filepath是共享驱动器位置