主题：关于CheckList未将对象引用设置到对象实例

Dim checkList As WinForm.CheckedListBox = e.Form.Controls("CheckedListBox1")
Dim dr As DataRow
dr = DataTables("员工信息表").Find(" [员工代号] = '"& _UserNo &"' ")
If dr IsNot Nothing Then
    For Index As Integer = 0 To checkList.Items.Count - 1
        checkList.SetItemChecked(Index, True)
    Next
End If

显示未将对象引用设置到对象实例怎么个情况