Nesting ASP.NET user controls programmatically

Question

I have a user control that programmatically includes a second user control several times, but the end result is that no HTML is generated for the controls at all.

Default.aspx

<%@ Page Language="vb" AutoEventWireup="false" CodeBehind="Default.aspx.vb" Inherits="TestApplication._Default" %>
<%@ Register TagName="Ten" TagPrefix="me" Src="~/Ten.ascx" %>

<html>
<head runat="server"></head>
<body>
    <form id="form1" runat="server">
        <me:Ten ID="thisTen" runat="server" />
    </form>
</body>
</html>

Ten.ascx

<%@ Control Language="vb" AutoEventWireup="false" CodeBehind="Ten.ascx.vb" Inherits="TestApplication.Ten" %>

<asp:Panel ID="List" runat="server"></asp:Panel>

Ten.ascx.vb

Public Class Ten
    Inherits System.Web.UI.UserControl
    Protected Sub Page_Init() Handles Me.Init
        For I As Integer = 0 To 11
            List.Controls.Add(New One(I.ToString))
        Next
    End Sub
End Class

One.ascx

<%@ Control Language="vb" AutoEventWireup="false" CodeBehind="One.ascx.vb" Inherits="TestApplication.One" %>

<asp:Button ID="OneButton" Text="Press ME!" runat="server" />

One.ascx.vb

Public Class One
    Inherits System.Web.UI.UserControl
    Private _number As String
    Sub New(ByVal number As String)
        _number = number
    End Sub
    Protected Sub OneButton_Click(ByVal sender As Object, ByVal e As EventArgs) Handles OneButton.Click
        Dim script As String = "<script type=""text/javascript"">" +
                               "alert('Button " + _number + "');" +
                               "</script>"
        ScriptManager.RegisterStartupScript(Me, Me.GetType(), "ServerControlScript", script, True)
    End Sub
End Class

Edit:

Using load control (Ten.aspx)

Dim p() As String = {I.ToString}
Dim o As One = Me.LoadControl(New One("").GetType, p)
List.Controls.Add(o)

Edit 2:

Dim o As One = Me.LoadControl("~/One.ascx")
o._number = I.ToString
List.Controls.Add(o)

Chris Gessler · Accepted Answer · 2012-07-10 04:23:07Z

1

I wouldn't perform this operation in the OnInit event, but this may or may not be related to your issue. Instead, I would load the controls in the OnLoad event.

However, using the new keyword is not typically how user controls are loaded. Sorry, but I only know C# and don't know the exact translation:

In C#:

One one = (One)this.LoadControl("~/Controls/One.ascx");

Does this look right in VB.NET?

Dim one As One = Me.LoadControl("~/Controls/One.ascx")

You'll likely have to delete the constructor and just set the property after you load the control.

edited Jul 10, 2012 at 4:23

answered Jul 10, 2012 at 4:12

Chris Gessler

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2 Comments

papodaca Over a year ago

Yes, this would work except that the constructor has a parameter. This causes a HttpCompileException. I was able to get past this by passing in the parameters in an array. However this does not solve the problem there is still no html generated.

Robert Beaubien Over a year ago

One note, if you want to handle events generated in the child control from the parent, you have to use the Page_Init event to create them. Otherwise the Page_Load event will work fine.

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