addAnnouncementCmd.CommandText = "insert into SYS_Announcement (Title) values(@Title) ;";
 addAnnouncementCmd.CommandText += "SELECT @ID=@@Identity;";
 addAnnouncementCmd.CommandType = CommandType.Text;
 addAnnouncementCmd.Parameters.Add("@Title", SqlDbType.NVarChar, 50);
 
SqlParameter oID = new SqlParameter("@ID", SqlDbType.Int);
oID.Direction = ParameterDirection.Output;
 addAnnouncementCmd.Parameters.Add(oID);
 
try
 {
 addAnnouncementCmd.Connection.Open(); 
 addAnnouncementCmd.ExecuteNonQuery();
 int addID = Convert.ToInt32(addAnnouncementCmd.Parameters["@ID"].Value.ToString());//addID新增的ID
 }
 finally
 {
 command.Connection.Close();
 }
4. 使用 ado.net 里面获取返回值的方法