asp.net 下拉触发错误事件

Question

我正在使用 VS 2010、.net 4、vb.net。我有一个 asp.net 网站，页面上有 2 个下拉列表。

  <asp:DropDownList ID="ddlClassIndex" runat="server" AutoPostBack="true" />
    <asp:DropDownList ID="ddlClassQBankList" runat="server" AutoPostBack="true" />

当页面首次加载时，我可以单击其中任何一个，选择一个项目，事件就会正确触发。当我选择任一下拉框作为第二个操作时，第一个下拉框 ddlClassIndex.SelectedIndexChanged 会触发。我到底做错了什么才会发生这样的事情。我在页面加载时执行 page.ispostback=false 检查，并且我们也使用母版页。

有什么想法吗？

当然..

 Private Sub LoadClass()
    Dim Os As List(Of Dempsey.OldeTestClassIndex) = Nothing
    Dim Oc As New Dempsey.OldeTestClassIndex_Controller
    Os = Oc._GetClassIndexData(0)

    Dim X = From w In Os
            Where w.Active = 3
            Select w

    Os = X.ToList

    With Me.ddlClassIndex
        .DataSource = Os.OrderBy(Function(o) o.ClassTitle)
        .DataTextField = "ClassTitle"
        .DataValueField = "tblClassIndexID"
        .DataBind()
        .Items.Insert(0, New ListItem("Choose Class Title", "0"))
        .SelectedIndex = 0
    End With


End Sub



Protected Sub ddlClassIndex_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles ddlClassIndex.SelectedIndexChanged
    If Me.ddlClassIndex.SelectedIndex > 0 Then
        If ClassHasCategories(Me.ddlClassIndex) = True Then
            Response.Redirect("AddEditQBank.aspx?ClassIndexID=" & Me.ddlClassIndex.SelectedItem.Value)
        Else
            Me.lblStatus.Text = "No Categories"
            Me.lblStatus.Visible = True
        End If

    End If
End Sub

Private Sub LoadClassQBankList()
    Dim ary As New ArrayList
    ary.Add(1)
    ary.Add(2)
    ary.Add(3)

    Dim Os As List(Of Dempsey.OldeTestClassIndex) = Nothing
    Dim Oc As New Dempsey.OldeTestClassIndex_Controller
    Os = Oc._GetClassIndexData(0)

    Dim X = From w In Os Join l In ary On w.Active Equals l
            Where w.KT = 1 And w.RandomTest = 1
                    Select w

    Os = X.ToList

    With Me.ddlClassQBankList
        .DataSource = Os.OrderBy(Function(o) o.ClassTitle)
        .DataTextField = "ClassTitle"
        .DataValueField = "tblClassIndexID"
        .DataBind()
        .Items.Insert(0, New ListItem("Choose Class Title", "0"))
        .SelectedIndex = 0
    End With

End Sub
Protected Sub ddlClassQBankList_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles ddlClassQBankList.SelectedIndexChanged
    If Me.ddlClassQBankList.SelectedIndex > 0 Then
        Response.Redirect("ClassQBankList.aspx" & "?ClassIndexID=" & Me.ddlClassQBankList.SelectedValue)
    End If
End Sub

~~~~~~~~~~ 更多信息 我正在检查页面回发。当我从下拉列表中选择时，它会重定向到不同的页面。当我单击后退按钮并在另一个下拉列表中选择另一个值时，两个 SelectedIndexChanged 都会触发。那么我需要对视图状态做一些事情吗？在我重定向到另一个页面之前？

Answer 1

超级老了，但对于那些仍然看到这个平淡答案的可怜人来说，你可能会在 Rick Strahl 的（同样老）的帖子中找到一些安慰：西风：ASP.NET ListBoxes、SelectedValue 和 ViewState。

剧透警告：这有点 hacky，涉及到进行一些您自己的视图状态管理。