using System;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace DQ
{
	public class DQTextBox : TextBox
	{
		private String header;

		public String Header
		{
			get
			{
				return header;
			}
			set
			{
				header = value;
			}
		}
	}

	public class TestContainer : UserControl
	{
		public DQTextBox Test
		{
			set
			{
				this.Controls.Add(value);
			}
		}

		protected override void RenderChildren(HtmlTextWriter render)
		{
			if(this.HasControls())
			{
				foreach(Control control in this.Controls)
				{
					DQTextBox dqTextBox = (DQTextBox)control;
					render.Write(String.Format("{0}: ", dqTextBox.Header));
					dqTextBox.RenderControl(render);
					render.RenderBeginTag(HtmlTextWriterTag.Br);
				}
			}
		}

		protected override void Render(HtmlTextWriter render)
		{
			render.RenderBeginTag(HtmlTextWriterTag.B);
			render.Write("test container:");
			render.RenderEndTag();
			render.RenderBeginTag(HtmlTextWriterTag.Br);
			this.RenderChildren(render);
		}
	}
}

<%@ Register TagPrefix="DQ" Namespace="DQ" Assembly="TestControl" %>

            <dq:TestContainer id="testContainer" runat="server">
                <test runat="server" Header="test0" id="Test0"></test>
                <test runat="server" Header="test1" id="Test1"></test>
                <test runat="server" Header="test2" id="Test2"></test>
            </dq:TestContainer>