Add control within server control tags when server control dropped in WebForm

See more:

C#

ASP.NET

server-control

Hi guys,
I had developed a server control which acts as a container (user can add any control inside the server control).

[DefaultProperty("Text")]
    [Designer(typeof(ContainerControlDesigner))]
    [ParseChildren(false)]
    [ControlBuilderAttribute(typeof(SampleControlBuilder))]
    [ToolboxData("<{0}:Sample  runat="server"></{0}:Sample>")]
    public class Sample: WebControl, INamingContainer
    {
protected override void CreateChildControls()
        {
            System.Collections.IEnumerator myEnumerator = items.GetEnumerator();
            while (myEnumerator.MoveNext())
                this.Controls.Add((TextBox)myEnumerator.Current);
        }

        protected override void AddParsedSubObject(Object obj)
        {
            if (obj is TextBox)
            {
                items.Add(obj);
            }
        }
    }
public class SampleControlBuilder : ControlBuilder
    {
        public override Type GetChildControlType(String tagName,
                                            IDictionary attributes)
        {
            if (String.Compare(tagName, "myitem", true) == 0)
            {
                return typeof(TextBox);
            }
            return null;
        }
    }

    public class SampleContainerControlDesigner : ContainerControlDesigner
    {
        public override bool AllowResize
        {
            get { return false; }
        }

        private Style _style = null;
ublic override string FrameCaption
        {
            get
            {
                return "Dynamic Page Loader";
            }
        }

        public override Style FrameStyle
        {
            get
            {
                if (_style == null)
                {
                    _style = new Style();
                    _style.Font.Name = "Verdana";
                    _style.Font.Size = new FontUnit("XSmall");
                    _style.BackColor = Color.LightBlue;
                    _style.ForeColor = Color.Black;
                }

                return _style;
            }
        }
    }

When the server control droped:

<cc1:Sample ID="Sample"  runat="server" />

When the user add some control to the server control:

<cc1:Sample ID="Sample"  runat="server" >
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
</cc1:Sample

Now, what I want is to add some controls within the server control tags just after the user had dropped the server control from toolbox into the webform asp.

How can I do this?????

Best regards :)