Programatically Load User Controls

The other day I was working on a code behind form and I needed to dynamically load a UserControl and access its properties. I was stumped, but with a little help from the codejunkies at aspnextgen.com I was able to move on. Here is a little sample to demonstrate this technique.

This sample consists of 3 pages:

  • default.aspx -- the standard ASP.NET page
  • cbDefault.vb -- the codebehind page for default.aspx
  • ucHeading.ascx -- a usercontrol with a property called page heading.

default.aspx simply has a panel object as a placeholder, and references the code behind file.

default.aspx

<%@ Page EnableSessionState="false" explicit="true" strict="true" MaintainState="false" inherits="cbDefault" src="cbDefault.vb"%>
<html>
<head>
<title></title>
</head>
<body bgcolor="#FFFFFF" >
<asp:panel id="pnlHeading" runat="server" />
</body>
</html>

ucHeading has a single property called PageHeading. PageHeading is a string that is used to display the heading of the page for the web surfer.

ucHeading.ascx

<script runat="server">
Private _pageheading as String = ""
Public Property PageHeading As String
Get
    Return _pageheading
End Get
Set
    _pageheading = value
End Set
End Property
</script>
<h1><%=_pageheading%></h1>

cdDefault.vb is the code behind file for default.aspx. It contains the meat of this demo. The logic of cbDefault.vb is:

  • Load the UserControl
  • Get the type of UserControl
  • Get access to the property "PageHeader"
  • Set the property "PageHeader"
  • Add the UserControl to the panel object on default.aspx

cbDefault.vb

Option Strict On
Option Explicit On

Imports System
Imports System.Reflection
Imports System.Web.UI
Imports System.Web.UI.WebControls

Public Class cbDefault : Inherits Page
Public pnlHeading as Panel

Public Sub Page_Load(Src As Object, E As EventArgs)
  ' Load the control
  Dim myUC as UserControl = LoadControl("ucHeading.ascx")

  ' Set the Usercontrol Type
  Dim ucType as Type = myUC.GetType()

  ' Get access to the property
  Dim ucPageHeadingProperty as PropertyInfo = ucType.GetProperty("PageHeading")

  ' Set the property
  ucPageHeadingProperty.SetValue(myUC,"Access a Usercontrol from Code Behind",Nothing)

  pnlHeading.Controls.Add ( myUC )
End Sub

End Class

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Comments

Dave Wanta

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