如何为sql表中一个自增字段添加记录
string   time1   =   DateTime.Now.ToString( "yyyy-MM-dd   ");
                      string   time2   =   DateTime.Now.AddMonths(2).ToString( "yyyy-MM-dd   ");
                      string   cmdtext1   =   "insert   into   lendrtnrec(id,userid,bookid,lendtime,bertntime)values( ' "   +     ???？？？     + " ' "+   readerid   +   " ', ' "   +   bookid   +   " ', ' "   +   time1   +   " ', ' "   +   time2   +   " ') ";
    id字段我想让它成为自增的，可是不会弄，同时，增加记录的时候，？？？？？处我不知道如何写，谁能教教我啊？

------解决方案--------------------
重新来过
SqlCommand cmd = new SqlCommand( "select max(id) from lendrtnrec ", yourconnectionstring);
int i = Convert.ToInt32(cmd.ExecuteScalar().ToString())+1;
你的？？？的地方就用i代替
------解决方案--------------------
string time1 = DateTime.Now.ToString( "yyyy-MM-dd ");
string time2 = DateTime.Now.AddMonths(2).ToString( "yyyy-MM-dd ");
string cmdtext1 = "declare @id as int ";
cmdtext1 += "select @id=max(id)+1 from lendrtnrec ";
cmdtext1 += "insert into lendrtnrec(id,userid,bookid,lendtime,bertntime)values(@id, "+ readerid + " ', ' " + bookid + " ', ' " + time1 + " ', ' " + time2 + " ') ";