必须定义参数'@myLeft'

Question

我的问题与已经回答的问题非常相似,但却没有.我想帮助整理一下.

我正在尝试将数据添加到数据库表,但我得到了标题错误.这是我的MySQL代码:

Dim objCmdInsert As New MySqlCommand("LOCK TABLE threads WRITE;SET @myLeft := lft;SELECT @myLeft FROM threads WHERE threadid = '" & Request.QueryString("id") & "';UPDATE threads SET rgt = rgt + 2 WHERE rgt > @myLeft;UPDATE threads SET lft = lft + 2 WHERE lft > @myLeft;INSERT INTO threads(threadid, category, userid, ipaddress, section, subject, summary, body, tags, postedat, updatedat, rating, status, lft, rgt) VALUES(?threadid, ?category, ?userid, ?ipaddress, ?section, ?subject, ?summary, ?body, ?tags, ?postedat, ?updatedat, ?rating, ?status, @myLeft + 1, @myLeft + 2);UNLOCK TABLES;", objConn)

objCmdInsert.Parameters.Add("?threadid", MySqlDbType.VarChar, 36).Value = Guid.NewGuid.ToString()
objCmdInsert.Parameters.Add("?category", MySqlDbType.VarChar, 36).Value = "articlecomment"
objCmdInsert.Parameters.Add("?ipaddress", MySqlDbType.VarChar, 20).Value = HttpContext.Current.Request.ServerVariables("REMOTE_ADDR")
objCmdInsert.Parameters.Add("?section", MySqlDbType.VarChar, 36).Value = DBNull.Value
objCmdInsert.Parameters.Add("?userid", MySqlDbType.VarChar, 36).Value = GetStubs.GetUserGuid(HttpContext.Current.User.Identity.Name.ToString())
objCmdInsert.Parameters.Add("?subject", MySqlDbType.VarChar, 500).Value = DBNull.Value
objCmdInsert.Parameters.Add("?summary", MySqlDbType.Text).Value = DBNull.Value
objCmdInsert.Parameters.Add("?body", MySqlDbType.Text).Value = CommentBody.Text
objCmdInsert.Parameters.Add("?tags", MySqlDbType.VarChar, 500).Value = DBNull.Value
objCmdInsert.Parameters.Add("?postedat", MySqlDbType.DateTime).Value = DateTime.Now.ToString()
objCmdInsert.Parameters.Add("?updatedat", MySqlDbType.DateTime).Value = DateTime.Now.ToString()
objCmdInsert.Parameters.Add("?rating", MySqlDbType.Int32).Value = "0"
objCmdInsert.Parameters.Add("?status", MySqlDbType.VarChar, 200).Value = "Open"

我究竟做错了什么？

Answer 1

我通过广泛的Google搜索MySQL中的未定义参数找到了解决这个问题的方法.本文(MySql.Data.MySqlClient.MySqlException:参数'@id'必须定义)涵盖了问题的基础知识.据我所知,这与连接器的升级有关.

您需要添加Allow User Variables=True连接字符串才能使用自定义变量.解决同样棘手的问题非常简单.;)