MySql 怪异问题Parameter '?applicantOperator' must be defined

程序里是这样写的：
if (applicantOperator != "")
{
  applicantOperatorClause = " AND applicantname like ?applicantOperator ";
}

cmd.Parameters.Add("?Applicantname", applicantOperator);

最后执行时却一直报错 “Parameter '?applicantOperator' must be defined”，经调试 applicantOperator 里面有值。applicantOperator的值是通过combox得到的，等待高人救场啊

补充一下是 winform + MySql的项目

cmd.Parameters.Add("?Applicantname", applicantOperator);

改成：
cmd.Parameters.Add("?applicantOperator", applicantOperator);