.net中单步执行没有问题，但是运行出错

 try
            {
                listmail = mailclass.MailSend(mailbody); // 返回已经发送的邮件ID列表(包括抄送和密抄)
                // listattfile  = AttUpload(mailbody.MailReceiverStr.ToString());   // 返回邮件附件数组
                foreach (string mailID in listmail)
                {   // 循环发送邮件附件
                    foreach (UDS.Components.MailAttachFile att in upattlist)
                    {   //　处理邮件附件的数据库操作部分                         Random TempNameInt = new Random();
                        string NewDocDirName = TempNameInt.Next(100000000).ToString();
                        Directory.CreateDirectory(Server.MapPath(".") + "\\AttachFiles\\" + Username + "\\" + NewDocDirName);
                                                File.Copy(Server.MapPath(".") + "\\" + att.FileVisualPath, Server.MapPath(".") + "\\AttachFiles\\" + Username + "\\" + NewDocDirName + "\\" + att.FileName, true);                                                att.FileVisualPath = "\\AttachFiles\\" + Username + "\\" + NewDocDirName + "\\" + att.FileName;
                        mailclass.AttSend(att, Int32.Parse(mailID));
                    }
                }
                if (cblistAttribute.Items[1].Selected && Request.Form["hdnProjectID"].ToString() != "0")
                {
                    DocProcess(mailbody, upattlist);
                }                Response.Write("<script language=javascript>alert('邮件发送成功!');if(parent.frames.length==0) window.close();else self.location=('Index.aspx');</script>");
            }
            catch (Exception sendex)
            {
                UDS.Components.Error.Log(sendex.ToString());
                Server.Transfer("../../Error.aspx");
            }文件“邮件.doc”正由另一进程使用，因此该进程无法访问该文件。"