guys i a m trying to build a webpage using c# as language in asp.net....

page consist of a button and i want is that when i click on that button a new textbox is added to the page dynamically on runtime..
My program works fine it adds a Textbox to the page ..but i want is that when i click again the button after clicking once i am able to add another text box but retaining the previous one...
but when i do that my previous one is lost

can any one please help me in this............


this is the code back file
Code:
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

public partial class _Default : System.Web.UI.Page 
{


    public bool IsControlAdded
         {
                get
              {
                                if (ViewState["IsControlAdded"] == null)
                                 ViewState["IsControlAdded"] = false;

     

            return (bool)ViewState["IsControlAdded"];

     

       }

       set
               {

           ViewState["IsControlAdded"] = value;

       }

   }

    

   protected void Page_Load(object sender, EventArgs e)

   {

       if(IsControlAdded)

           AddUserControl();

   }

    
















    protected void btnLoad_Click(object sender, EventArgs e)
    {
        if (!IsControlAdded) AddUserControl();
    }
    protected void btnSubmit_Click(object sender, EventArgs e)
    {

    }
    TextBox t; static int x=0;
    private void AddUserControl()
    {
        x =x+ 50;

        t = new TextBox();
        t.ID = Convert.ToString(x);
        t.Style.Add("position", "Relative");
        t.Style.Add("runat", "server");
        t.Style.Add("left", "" + x + "px");
        t.Style.Add("top", "" + x + "px");
        


        Page.Form.Controls.Add(t);
        IsControlAdded = true;

    }
}