MySql. MySqlException: Parameter '??' must be defined.解决办法
MySql.Data.MySqlClient.MySqlException:“Fatal error encountered during command execution.”
内部错误：MySqlException: Parameter '??' must be defined.解决办法
内部错误：MySqlException: Parameter '??' must be defined.解决办法
ERROR 执行数据库查询时出错：
MySql.Data.MySqlClient.MySqlException (0x80004005): Fatal error encountered during command execution.
---> MySql.Data.MySqlClient.MySqlException (0x80004005): Parameter '@i' must be defined.
at MySql.Data.MySqlClient.Statement.SerializeParameter(MySqlParameterCollection parameters, MySqlPacket packet, String parmName, Int32 parameterIndex)
at MySql.Data.MySqlClient.Statement.InternalBindParameters(String sql, MySqlParameterCollection parameters, MySqlPacket packet)
at MySql.Data.MySqlClient.Statement.BindParameters()
at MySql.Data.MySqlClient.PreparableStatement.Execute()
at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior)
解决方法：连接字符串加入 : Allow User Variables=True;
Fatal error encountered during command execution解决办法举例：
之前连接串：
Host=localhost;UserName=root;Password=20211111;Database=20211111;Port=3306;CharSet=utf8;Allow Zero Datetime=true;
修改后连接串：
Host=localhost;UserName=root;Password=20211111;Database=20211111;Port=3306;CharSet=utf8;Allow Zero Datetime=true; Allow User Variables=True;
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