重复载入图片

图片由FTP下载下来，再填充到pictureBox，发现第一次载入可以，但是重复载入时就提示该文件正在一个进程访问，
请教一个这个问题怎么解决，3Q   private void Download(string filePath, string fileName)
        {
            FtpWebRequest reqFTP;
                       try
            {
                FileStream outputStream = new FileStream(filePath + "\\" + fileName, FileMode.Create);                reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri("ftp://" + ftpServerIP + "/" + fileName));                reqFTP.Method = WebRequestMethods.Ftp.DownloadFile;                reqFTP.UseBinary = true;                reqFTP.Credentials = new NetworkCredential(ftpUserID, ftpPassword);                FtpWebResponse response = (FtpWebResponse)reqFTP.GetResponse();                Stream ftpStream = response.GetResponseStream();                long cl = response.ContentLength;                int bufferSize = 2048;                int readCount;                byte[] buffer = new byte[bufferSize];                readCount = ftpStream.Read(buffer, 0, bufferSize);                while (readCount > 0)
                {
                    outputStream.Write(buffer, 0, readCount);                    readCount = ftpStream.Read(buffer, 0, bufferSize);
                }                ftpStream.Close();                outputStream.Close();                response.Close();                ftpStream.Dispose();
                outputStream.Dispose();
                GC.SuppressFinalize(this);            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
           
        }   string filePathAndName = "E:\\StuPhoto" + DateTime.Now.ToString("yyyy-MM-dd-hh-mm-ss") + ".jpg";
                Download("E:\\StuPhoto", this.txtSearchInputStuID.Text + ".jpg");
                System.Drawing.Image tempStuPhoto = (System.Drawing.Image)(Bitmap.FromFile(("E:\\StuPhoto\\" + this.txtSearchInputStuID.Text + ".jpg")));
                System.Drawing.Image stuPhoto = (System.Drawing.Image)(tempStuPhoto.Clone());
                tempStuPhoto.Dispose();
                this.picBoxStuPhoto.Image = stuPhoto;
高手帮看看什么问题，或者有什么解决办法