Custom server control render method

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ASP.NET

I am creating custom server control. I have two classes in project.
One is main class that render control and another will be used to render content based on condition.

I just want to know how to render content from other classes in main class.
For example. This is just an example.
My main class code:

[ParseChildren(true, "TopLeft_Pane")]
   [DefaultProperty("InnerHTML")]
   [ToolboxData("<{0}:MyControl runat=server>")]
   public class Class1 : WebControl
   {
   [Bindable(true)]
       [Category("Appearance")]
       [DefaultValue("")]
       [Localizable(true)]
       public string InnerHTML
       {
           get
           {
               String s = (String)ViewState["Text"];
               return ((s == null) ? "[" + this.ID + "]" : s);
           }

           set
           {
               ViewState["Text"] = value;
           }
       }

   /* TopLeftPane is my another class and I create an object here */
   private TopLeftPane _topleftpane;
       public TopLeftPane TopLeft_Pane
       {
           get
           {
               if (_topleftpane == null)
                   _topleftpane = new TopLeftPane();
               return _topleftpane;
           }
       }

   protected override void CreateChildControls()
       {
           this.Controls.Add(TopLeft_Pane);
       }

   protected override void Render(HtmlTextWriter writer)
       {
           AddAttributesToRender(writer);

           writer.AddAttribute(HtmlTextWriterAttribute.Cellpadding,
               "1", false);
       /* Begin Table */
           writer.RenderBeginTag(HtmlTextWriterTag.Table);

       /* Begin TD */
           writer.RenderBeginTag(HtmlTextWriterTag.Tr);

           /* Begin TD */
           writer.RenderBeginTag(HtmlTextWriterTag.Td);

           /* Rendering content from TopLeftPane class*/
       TopLeft_Pane.RenderControl(writer)

       writer.RenderEndTag();
       /* End TD */

       writer.RenderEndTag();
       /* End TR */

       writer.RenderEndTag();
       /* End Table */
   }

   }

   My TopLeftPane class

   [ParseChildren(true)]
   [PersistChildren(false)]
   public class TopLeftPane : WebControl
   {
       public TopLeftPane(): base(HtmlTextWriterTag.Div)
       {
       }
       private string _headertitle;
       public string HeaderTitile
       {
           get { EnsureChildControls(); return _headertitle; }
           set { EnsureChildControls(); _headertitle = value; }
       }
       protected override void CreateChildControls()
       {
           Controls.Add(new LiteralControl(HeaderTitile));
       }
       protected override void Render(HtmlTextWriter writer)
       {
           writer.Write(this.HeaderTitile);
       }
   }

My page code on page load event:

MyControl.TopLeftPane top = new MyControl.TopLeftPane();
top.HeaderTitile = "Header title";

When I run the page, Header title always getting null.

This is a just sample code. I will have more than 20 classes so I dont want to write a code in main class to render whole control.

I hope all of you understand my problem. Any articles or suggetion would be greatly appreciate.