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POButton in UpdatePanel Randomly Loses Event Handler
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  1. POButton in UpdatePanel Randomly Loses Event Handler
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    copied!<p>On an ASP.NET web page, I have an UpdatePanel. Inside this UpdatePanel, I have an "Add" button which dynamically adds any number of a User Control that I have created to a PlaceHolder. The User Control contains a label, a button, and a 3rd-party control. The button inside the User Control is for removing that particular User Control from the parent panel. Both the "Add" and "Remove" functionality work correctly. However, the event handler on the Add button sometimes stops working with no apparent pattern or cause. If I add 2 UCs and remove 1, sometimes the Add button continues to work and sometimes it doesn't. Any step toward finding a cause would be helpful.</p> <p>For context, the UCs are called "Whereas" because they are WHEREAS clauses in resolutions. Here is the code, cut down to relevant content only:</p> <p><strong>Edit.aspx</strong></p> <pre><code>... &lt;asp:ScriptManager ID="sm1" runat="server"&gt;&lt;/asp:ScriptManager&gt; &lt;asp:Panel ID="pnlMain" runat="server"&gt; &lt;div class="form-horizontal"&gt; &lt;asp:UpdatePanel ID="upnlWhereas" runat="server"&gt; &lt;ContentTemplate&gt; &lt;asp:PlaceHolder ID="phWhereas" runat="server"&gt;&lt;/asp:PlaceHolder&gt; &lt;div class="control-group"&gt; &lt;asp:Label ID="lblAddWhereas" AssociatedControlID="btnAdd1Whereas" CssClass="control-label" runat="server"&gt;&lt;/asp:Label&gt; &lt;div class="controls"&gt; &lt;asp:Button ID="btnAdd1Whereas" CssClass="btn" UseSubmitBehavior="false" Text="Add Whereas" runat="server" /&gt; &lt;/div&gt; &lt;/div&gt; &lt;/ContentTemplate&gt; &lt;/asp:UpdatePanel&gt; &lt;/div&gt; &lt;/asp:Panel&gt; ... </code></pre> <p><strong>Edit.aspx.vb</strong> (class is Edit2)</p> <pre><code>... 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 ... </code></pre> <p><strong>Whereas.ascx.vb</strong></p> <pre><code>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 </code></pre>
 

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