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POASP.NEt WebForms UserControl: Why is overriding .Visible causing a System.StackOverflowException?
 

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  1. POASP.NEt WebForms UserControl: Why is overriding .Visible causing a System.StackOverflowException?
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    <p>I have a custom UserControl whose .Visible property I need to set to True or False. However, if the UserControl's first child control is a Panel and its ID is cMain, I want it to set the Panel's .Visible property instead of the UserControl's. Here's my code:</p> <p>Here's the custom class I use:</p> <pre><code>Public MustInherit Class MyControl : Inherits UserControl Public Overrides Property Visible As Boolean Get Return GetVisible() End Get Set(value As Boolean) SetVisible(value) End Set End Property Function GetVisible() As Boolean Dim c As Control = GetMain() If TypeOf c Is Panel Then Return c.Visible Else Return MyBase.Visible End If End Function Sub SetVisible(Value As Boolean) Dim c As Control = GetMain() If TypeOf c Is Panel Then c.Visible = Value Else MyBase.Visible = Value End If End Sub Function GetMain() As Control Dim c As Control = If(Controls.Count = 0, Nothing, Controls(0)) If Not (TypeOf c Is Panel AndAlso c.ID = "cMain") Then c = Me Return c End Function End Class </code></pre> <p>Here's the actual UserControl itself:</p> <pre><code>&lt;%@ Control Language="vb" AutoEventWireup="false" CodeBehind="TestControl.ascx.vb" Inherits="JsonJqueryDevex.TestControl1" %&gt; &lt;asp:Panel ID="cMain" runat="server"&gt; inside &lt;/asp:Panel&gt; outside </code></pre> <p>UserControl's codebehind:</p> <pre><code>Public Class TestControl1 Inherits MyControl Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load End Sub End Class </code></pre> <p>Here's the markup to implement it into the host page:</p> <pre><code>&lt;uc:TestControl ID="ucTest" Visible="true" runat="server"&gt;&lt;/uc:TestControl&gt; </code></pre> <p>Notice that I overrode .Visible within my base clase. I did this so that I could call MyBase if the control being referenced is the UserControl itself. Otherwise, I assume it's the Panel control. When I load the page, I get <code>System.StackOverflowException</code>. What's funny is that I don't get this when I have the custom control's Visible property set to <code>false</code> in the markup.</p> <p>The stack trace shows that it's getting caught in .Visible's get accessor when it calls <code>Return GetVisible()</code>. If it's a Panel, it will execute <code>Return c.Visible</code>. However, as soon as I reference .Visible when c is a Panel, it breaks back into MyControl's .Visible get accessor. I don't know how this is possible since I am only overriding my custom control's Visible property, but it's acting as if I am overriding the Panel's .Visible property. What is going on here?</p>
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    1. USoscilatingcretin
    1. USoscilatingcretin
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      1. VTUpMod
    1. COHave you set breakpoints? What is the value of `Controls(0)` within your `GetMain()` method? Often times static text in the markup (even whitespace) can end up as a `LiteralControl` in the `Controls` collection. If this is your case, then your condition will always return `Me`, thus the infinite loop and cause of `StackOverflowException`
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      1. POASP.NEt WebForms UserControl: Why is overriding .Visible causing a System.StackOverflowException?
      1. USMike Guthrie
    2. CONo, it is the Panel for sure. As you can see in the code, I force it to check the type and also the ID.
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      1. POASP.NEt WebForms UserControl: Why is overriding .Visible causing a System.StackOverflowException?
      1. USoscilatingcretin
 

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