FindControl for nested controls in UserControl returns null

I have a very weird issue. I have a UserControl that has some controls inside. I want to refer those controls after, in another postback. But when I try to get them the Controls property of my controls returns null. I'm working on vs2008.

Here is the sample code:

public partial class MyUserControl : System.Web.UI.UserControl, INamingContainer
{
    protected void Page_Load(object sender, EventArgs e)
    {
        foreach (Control control in this.Controls)
        {
            Response.Write(control.ClientID);
        }
    }

    private void MyTable()
    {
        Table table = new Table();
        TableRow row = new TableRow();
        TableCell cell = new TableCell();

        CheckBox check = new CheckBox();
        check.ID = "theId";
        check.Text = "My Check";
        check.AutoPostBack = true;
        cell.Controls.Add(check);
        row.Cells.Add(cell);

        check = new CheckBox();
        check.ID = "theOther";
        check.AutoPostBack = true;
        check.Text = "My Other Check";

        cell = new TableCell();
        cell.Controls.Add(check);
        row.Cells.Add(cell);

        table.Rows.Add(row);
        this.Controls.Add(table);
    }

    protected override void Render(HtmlTextWriter writer)
    {
        MyTable();
        base.Render(writer);
    }
}

and the Default.aspx page is something like:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.cs" Inherits="Tester.Default" %>
<%@ Register TagPrefix="uc1" TagName="MyControl" Src="~/MyUserControl.ascx" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Unbenannte Seite</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <uc1:MyControl ID="MyControlInstance" runat="server" />
    </div>
    </form>
</body>
</html>

I don't know if I'm lost in some part of the ASP.NET life cycle. But this situation is making me crazy. Any help would be very grateful.

Solution

Create your child controls (MyTable) in either CreateChildControls or OnInit:

protected override void CreateChildControls()
{
    MyTable();
    base.CreateChildControls();
}

protected override void OnInit(object sender, EventArgs e) 
{
    MyTable();
    base.OnInit(e);
}

You shouldn't/cannot create controls in Render as it occurs after Page_Load. See the ASP.Net Page Lifecycle here.