ASP.NET - 回滚事务

SqlConnection con =new SqlConnection(ConnectionDb.conStr);//获取数据库连接
con.Open();//打开连接
SqlTransaction sqltra = con.BeginTransaction();//开始事务
SqlCommand cmd =new SqlCommand();//实例化
cmd.Connection = con;//获取数据连接
cmd.Transaction = sqltra;//，在执行SQL时，
try
{
string sql ="insert into OA_MEETING(meeting_id,meeting_name,meeting_title,start_time,end_time,announce_time,explain,reg_emp_id,emc_emp_id,par_emp_id,rep_emp_id,participate,MEETING_TYPE,PROJ_ID,WORK_ID)values('"+ id +"',N'"+ meetname +"',N'"+ meettitle +"','"+ starttime +"','"+ endtime +"',N'"+ djtime +"',N'"+ meetinfo +"','"+ empid +"','"+ meetperson +"','"+ lname +"','"+ writer +"','"+ ccname +"','"+ hidsort.Value +"','"+ proid +"','"+ workid +"')";
cmd.CommandText = sql;
cmd.ExecuteNonQuery();

//string meetid = id;
int size =0;
HttpFileCollection files = HttpContext.Current.Request.Files;
//遍历上传文件窗体所有Html控件
foreach (string NameId in Request.Form)
{
//找到控件ID名前四位为"txt_"的文件说明文本框
if (NameId.Substring(0, 4) =="ttx_")
{
//获取文本说明
if (Request.Form[NameId] !="")
{
string Explain = Request.Form[NameId];//获取txt文本说明

HttpPostedFile pstfile = files["fil_"+ NameId.Substring(4)];
string fileName ="";
string fileExtension ="";
fileName = System.IO.Path.GetFileName(pstfile.FileName);//上传的文件全名
fileExtension = System.IO.Path.GetExtension(fileName);//扩展名
string NewName = fileName.Remove(fileName.LastIndexOf("."));//去掉后缀名的文件名
string sql1 ="select isnull(max(app_id),0) from OA_MEETING_APPENDIX";

int idd = Convert.ToInt32(objConnction.getString(sql1)) +1;
ua.Folder_Exists("Meeting");
string filepath ="..\\AtthFiles\\Meeting\\Meeting_"+ idd.ToString() + fileExtension;
string sqlstr1 ="insert into OA_MEETING_APPENDIX(APP_ID,MEETING_ID,EXPLAIN,APP_PATH) values('"+ idd +"','"+ id +"',N'"+ Explain +"',N'"+ filepath +"')";
cmd.CommandText = sqlstr1;

int num = cmd.ExecuteNonQuery();
if (num >0)
{
pstfile.SaveAs(Server.MapPath("..\\AtthFiles\\Meeting\\Meeting_"+ idd.ToString() + fileExtension));
size = pstfile.ContentLength /1024;
objDocument.InsertDoc(5, idd, Explain, "", "", DateTime.Now.ToString("yyyy-MM-dd"), Convert.ToInt32(HempID.Value), filepath, size, hidwork.Value, hidpro.Value);
}
}
}
}
sqltra.Commit();
}catch(Exception ex)
{
sqltra.Rollback();
}