Library code snippets
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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however define an interface in your app_code directory that simply defines all of the properties that you want in your control, have your control implement this interface then when you load the control you can access the properties like so in the page where the control is loaded:
Control yourcontrol = LoadControl("UI/YourControl.ascx");
((IYourInterface)expander).Property = "some string";
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