请教各位一个关于HtmlControls与JavaScript的疑问

先上代码：

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<!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>无标题页</title>
</head>
<body>
<script type="text/javascript" language="javascript">
function doo()
{

    //javascript修改值和CodeBehinds中修改的效果一致？
   document.getElementById('inputText').value="asdf";
   document.form1.submit();
}
</script>
    <form id="form1" runat="server">
    <div>
      <asp:FileUpload id="fileUpload" runat="server" />
      <br />
      inputText1:<input type="text" id="inputText1" name="inputText1" runat="server" maxlength="12" />
      <br />
      inputText:<input type="text" enableviewstate="false" id="inputText" name="inputText" runat="server" maxlength="12" />
      <br />
      <input type="button" id="btnAdd" name="btnAdd" runat="server" onclick="doo()" value="添加" />
    </div>
    </form>
</body>
</html>

---CodeBehinds

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
{
    protected void Page_PreLoad(object sender,EventArgs e)
    {        //已经将inputText的enableSessionState设为false,这里为什么还可以获取到它的值？
        inputText1.Value = inputText.Value;
    }
    protected void Page_Load(object sender, EventArgs e)
    {
        Response.Write(this.IsPostBack.ToString()+"<br />");
        Response.Write(inputText.Value);
        inputText.Value = "xu test";
    }
}