无法定义事务，为何?

Question

   OleDbTransaction tran = con.BeginTransaction();
                str = string.Format(@"insert into Fillcards (strOldNumber,strNew numbers,strCardName,strOriginal,strHandlingpeople) values('{0}','{1}','{2}','{3}','{4}')", dr[0], newCardNum, dr[1], dr[2], handlingPeople);
                OleDbCommand com = new OleDbCommand(str, con);
                com.ExecuteNonQuery();
                com.Transaction = tran;
                str = string.Format(@"update Newcards set strNumber = '{0}' where strIDCard = '{1}'",newCardNum,ID);
                com = new OleDbCommand(str, con);
                com.ExecuteNonQuery();
                com.Transaction = tran;
                try
                {
                    tran.Commit();
                    return 1;
                }
                catch (Exception e)
                {
                    tran.Rollback();
                    return 4;
                }
                finally
                {
                    dr.Close();
                }
编译器错误信息: CS1023: 嵌入的语句不能是声明或标记语句源错误: 行 82:             //{
行 83:                 //开始事务
行 84:                 OleDbTransaction tran = con.BeginTransaction();
行 85:                 str = string.Format(@"insert into Fillcards (strOldNumber,strNew numbers,strCardName,strOriginal,strHandlingpeople) values('{0}','{1}','{2}','{3}','{4}')", dr[0], newCardNum, dr[1], dr[2], handlingPeople);
行 86:                 OleDbCommand com = new OleDbCommand(str, con);
 

Answer 1

  OleDbTransaction tran  = new OleDbTransaction ()
tran = con.BeginTransaction(); 

Answer 2

 实例化了，突然又好的,上面事务错了，不是那么用的。
正确方法
  str = string.Format(@"insert into Fillcards (strOldNumber,strNewnumbers,strCardName,strOriginal,strHandlingpeople) values('{0}','{1}','{2}','{3}','{4}')", dr[0].ToString(), newCardNum, dr[1].ToString(), dr[2].ToString(), handlingPeople);
                OleDbCommand com = new OleDbCommand(str, con);
                com.Transaction = tran;
                com.ExecuteNonQuery();
    str = string.Format(@"update Newcards set strNumber = '{0}' where strIDCard = '{1}'", newCardNum, ID);
                com.CommandText = str;
                com.ExecuteNonQuery();
   tran.Commit();