小弟新学，ORA-01008: 并非所有变量都已关联 --的问题

[kaikaichen]

ORA-01008: 并非所有变量都已关联
下面是代码，检查不出，哪个变量没赋值关联啊。小弟新手，谢谢指教。

protected void btChangeProc_Click(object sender, EventArgs e)
    {

        string CaseId = Request["CaseId"];
        string AptdDept = ddlDeptId.SelectedValue.ToString();
        string AptdUser = ddlProcUser.SelectedValue.ToString();


        OracleConnection cn = new OracleConnection(OracleHelper.ConnectionStringLocalTransaction); 
        OracleCommand cmd = new OracleCommand("UPDATE O_C_CaseRecord set APTDDEPT= :AptdDept, APTDUSER = :AptdUser, STATE = 'null' WHERE CASEID= :CaseId ",cn); 

        cn.Open(); 
       
        //执行命令
        int val = cmd.ExecuteNonQuery();
        cmd.Parameters.Clear();
        //判断是否修改成功
        if (val > 0)
            btChangeProc.Text = "移交成功";
        else
            btChangeProc.Text = "移交失败";

        cn.Close(); 
        
        
    }
}

报错：
+ $exception {"ORA-01008: 并非所有变量都已关联\n"} System.Exception {System.Data.OracleClient.OracleException}
+ this {ASP.memberpages_operm_case_chgcaseproc_aspx} MemberPages_OperM_Case_ChgCaseProc {ASP.memberpages_operm_case_chgcaseproc_aspx}
+ sender {Text = "确认移交"} object {System.Web.UI.WebControls.Button}
+ e {System.EventArgs} System.EventArgs
CaseId " 2008121110" string
AptdDept "1" string
AptdUser "jiangxy" string
+ cn {System.Data.OracleClient.OracleConnection} System.Data.OracleClient.OracleConnection
- cmd {System.Data.OracleClient.OracleCommand} System.Data.OracleClient.OracleCommand
+ base {System.Data.OracleClient.OracleCommand} System.Data.Common.DbCommand {System.Data.OracleClient.OracleCommand}
CommandText "UPDATE O_C_CaseRecord set APTDDEPT= :AptdDept, APTDUSER = :AptdUser, STATE = '待处理' WHERE CASEID= :CaseId " string
CommandTimeout 0 int
CommandType Text System.Data.CommandType
+ Connection {System.Data.OracleClient.OracleConnection} System.Data.OracleClient.OracleConnection
DesignTimeVisible true bool
+ Parameters {System.Data.OracleClient.OracleParameterCollection} System.Data.OracleClient.OracleParameterCollection
+ Transaction null System.Data.OracleClient.OracleTransaction
UpdatedRowSource Both System.Data.UpdateRowSource
+ 静态成员
+ 非公共成员
val 0 int

[kaikaichen]

代码中的 STATE = 'null' 修改过了，STATE = '待处理' 也一样这个报错。

[juxianxiang]

如何解决得？