asp.net - UpdatePanel中的按钮随机丢失事件处理程序

Question

在ASP.NET网页上，我有一个UpdatePanel。在此UpdatePanel内部，我有一个“添加”按钮，该按钮可将我创建的任意数量的用户控件动态添加到PlaceHolder中。用户控件包含标签，按钮和第三方控件。用户控件内的按钮用于从父面板中删除特定的用户控件。 “添加”和“删除”功能均正常工作。但是，“添加”按钮上的事件处理程序有时会停止工作，没有明显的模式或原因。如果我添加了2个UC并删除了1个，则“添加”按钮有时会继续起作用，有时却不会。找出原因的任何步骤都是有帮助的。

对于上下文，UC被称为“Whereas”，因为它们是决议中的WHEREAS子句。这是代码，仅缩减至相关内容:

Edit.aspx

...
<asp:ScriptManager ID="sm1" runat="server"></asp:ScriptManager>
<asp:Panel ID="pnlMain" runat="server">
    <div class="form-horizontal">
        <asp:UpdatePanel ID="upnlWhereas" runat="server">
            <ContentTemplate>
                <asp:PlaceHolder ID="phWhereas" runat="server"></asp:PlaceHolder>
                <div class="control-group">
                    <asp:Label ID="lblAddWhereas" AssociatedControlID="btnAdd1Whereas" CssClass="control-label" runat="server"></asp:Label>
                    <div class="controls">
                        <asp:Button ID="btnAdd1Whereas" CssClass="btn" UseSubmitBehavior="false" Text="Add Whereas" runat="server" />
                    </div>
                </div>
            </ContentTemplate>
        </asp:UpdatePanel>
    </div>
</asp:Panel>
...

Edit.aspx.vb (类为Edit2)

...
Private Property ControlsList As List(Of String)
    Get
        If ViewState("ControlsList") Is Nothing Then
            ViewState("ControlsList") = New List(Of String)
        End If

        Return CType(ViewState("ControlsList"), List(Of String))
    End Get
    Set(ByVal Value As List(Of String))
        ViewState("ControlsList") = Value
    End Set
End Property

Private ReadOnly Property NextID As Integer
    Get
        Return ControlsList.Count + 1
    End Get
End Property

Protected Overrides Sub LoadViewState(savedState As Object)
    MyBase.LoadViewState(savedState)

    For Each waID As String In ControlsList
        Dim NewWhereas As Whereas
        NewWhereas = Me.LoadControl("~/UserControls/Whereas.ascx")

        NewWhereas.ID = waID
        phWhereas.Controls.Add(NewWhereas)

        AddHandler NewWhereas.OnRemoveWhereasClick, AddressOf Whereas_OnRemoveWhereasClick
    Next
End Sub

...

Private Sub btnAdd1Whereas_Click(sender As Object, e As System.EventArgs) Handles btnAdd1Whereas.Click
    Dim NewWhereas As Whereas
    NewWhereas = Me.LoadControl("~/UserControls/Whereas.ascx")

    NewWhereas.ID = "wa" + NextID.ToString
    phWhereas.Controls.Add(NewWhereas)

    ControlsList.Add(NewWhereas.ID)
End Sub

Private Sub Whereas_OnRemoveWhereasClick(ByVal sender As Object)
    Dim thisButton As Button = sender
    Dim thisWhereas As Whereas = thisButton.Parent.Parent

    phWhereas.Controls.Remove(thisWhereas)
    ControlsList.Remove(thisWhereas.ID)
End Sub
...

，而asasx.vb

Public Delegate Sub ActionClick(ByVal sender As Object)

Public Class Whereas
    Inherits System.Web.UI.UserControl

    ...

    Public Event OnRemoveWhereasClick As ActionClick

    Public Sub btnRemoveWhereas_Click(ByVal sender As Object, ByVal e As EventArgs)
        RaiseEvent OnRemvoeWhereasClick(sender)
    End Sub
End Class

Answer 1

当文档大纲更改时，“更新”面板的行为通常会很奇怪。
尝试将“添加”按钮移到面板外，然后在更新面板的“触发器”部分中添加按钮。