Dynamically adding a user control to a repeater

Question

I have a class (MyClass) which represents a nested hierarchy, so the class has a property which is a collection of MyClass. MyClass also has a title property

To show it on a web page, I was hoping to create a user control which had a repeater. In the item template I would have literal to display the title property, and on the ItemCreated event of the repeater, I would create a new instance of the usercontrol, and add it into the current item in the repeater.

My problem is, when the Page_Load event in the usercontrol fires, if the control was dynamically added, the repMyClass repeater poroperty is null, even if I call EnsureChildControls. Am I missing something here? If I create a repeater and drop my userctonrol in the item template it works fine. My can't I get this to work dynamically?

User Control:

<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="MyControl.ascx.cs" Inherits="MyControl" %>
Items:<br/>
<asp:Repeater ID="repMyClass" runat="server" EnableViewState="false" 
    OnItemCreated="repMenuItems_ItemCreated">
    <HeaderTemplate><ul><HeaderTemplate>
    <ItemTemplate>
        <li><%# Eval("Title") %>
            <div><asp:PlaceHolder ID="SubItemPlaceholder" runat="server" /></div>
        </li></ItemTemplate>
    <FooterTemplate></ul></FooterTemplate>
</asp:Repeater>

User Control Code:

public partial class MyControl: System.Web.UI.UserControl
{
    public IEnumerable<MyClass> ChildItems { get; set; }
    protected void Page_Load(object sender, EventArgs e)
    {
        this.repMyClass.DataSource = ChildItems;
        this.repMyClass.DataBind();
    }

    protected void repMenuItems_ItemCreated(object Sender, RepeaterItemEventArgs  e)
    {
        if (e.Item.ItemType == ListItemType.AlternatingItem || e.Item.ItemType == ListItemType.Item)
        {
            //Get the MyClass instance for this repeater item
            MyClass mcCurrent = (MyClass)e.Item.DataItem;

            //If the MyClass instance has child instances
            if (mcCurrent.Children != null && mcCurrent.Children.Length > 0)
            {
                //Add a new user control and set it's property so it can bind
                PlaceHolder ph = (PlaceHolder)e.Item.FindControl("SubItemPlaceholder");

                MyControl ctl = (MyControl)Page.LoadControl(typeof(MyControl),new object[] {});

                ctl.ChildItems = mcCurrent.Children;
                ph.Controls.Add(ctl);
            }
        }
    }
}

Solution

I had done this a long time ago for creating nested reports using Accordions.

In Index, when you want to dynamically add User Control instances:

// Declare Placeholder    
PlaceHolder ph = (PlaceHolder)e.Item.FindControl("SubItemPlaceholder")

// Adding some literal controls to header
ph.Controls.Add(new LiteralControl("This is the accordion header!!"));

// Declare new control variable
crt = new Control();

// Load up your User Control
crt = LoadControl("~/MyControl.ascx");

// Check if it has loaded properly
if (crt != null)
{
    // GET / SET any custom properties of the User Control
    ((myClass)crt).title = "Welcome";

    // Add the new User Control to the placeholder's controls collection
    ph.Controls.Add(crt);
}

Note: In the User Control, you must add the "ClassName" in the declaration tag

<%@ Control Language="C#" AutoEventWireup="true" CodeFile="MyControl.ascx.cs" Inherits="myTest" ClassName="myClass" %>

Also, any properties you wish to expose when creating instances dynamically, you declare them as follows:

public string title { get; set; }

So if you want to force a value when creating for "repMyClass" you can set it as a property and assign whatever value you want to it programmaticaly.

Comments

[Jeremy]

The problem is, my user control has it's own child controls (a repeater in this case). In the page_load event of the user control, the repeater variable is actually null. I can't set it myself, the asp.net framework needs to.

[Jeremy]

The problem is, my user control has it's own child controls (a repeater in this case). In the page_load event of the user control, the repeater variable is actually null. I can't set it myself, the asp.net framework needs to.

[vvohra87]

@Jeremy : Sure you can. Just create a property of type repeater. You can then access it, instantize it, do whatever you want with it. Please clarify - according to me you should have a public property in the UserControl, in the Page Load of the UserControl you should be using that public property to bind data to the repeater. Is that correct?

[Meligy]

The theory is that you shouldn't need to use the load, use the setter instead. Another alternative is in the answer update, that one might fix the issue. I think the problem is the event used, this has very good probability of being the issue.