Listview中的下拉列表的SelectedIndexChanged事件未发生。在用户控件中

Question

我有一个ListView和DropDownList（主要），并且在ListView的每一行内都有一个和一个文本框。全部在用户控件上，并在另一个usercontol上使用此用户控件（这里是要执行的操作。）（我们使用的是DNN）。  现在我想为dropdownlist添加事件处理程序，它将对SelectedIndexChanged作出反应。我想显示和隐藏其他下拉列表和文本框，具体取决于所选DropDrownList（主要）的特定值。 我无处可去。尽管有几次尝试。

                                                                                                                                                                                                                                                                                                                                                               筛选结果：＆amp; nbsp                                                                                                                                                                                                             评论：                                                                                                                                                                                                                                                                        使用的子集：＆amp; nbsp                                                                                                                                                                                                                                                                                                              TAR状态：＆amp; nbsp                                                                                                                                                                                                                                                                                                                                                                                

这样的代码

Public Sub ddlFindingsScreeningOutcome_SelectedIndexChanged（ByVal sender As Object，ByVal e As EventArgs）             Dim ddl As DropDownList = CType（sender，DropDownList）

        Dim item As ListViewItem = CType(ddl.NamingContainer, ListViewItem)

        Dim txtFindingsComments As TextBox = CType(item.FindControl("txtFindingsComments"), TextBox)
        Dim ddlFindingsTarStatus As DropDownList = CType(item.FindControl("ddlFindingsTarStatus"), DropDownList)

        If Not ddl Is Nothing Then
            If Not ddl.SelectedItem.Text = "Not Screened" Then
                txtFindingsComments.Visible = True
                ddlFindingsTarStatus.Visible = True

            End If
        Else
            txtFindingsComments.Visible = False
            ddlFindingsTarStatus.Visible = False
        End If


    End Sub