Adesso forse ho capito cosa vuoi fare.
Ecco qui un piccolo esempio:

Codice PHP:
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="Forum._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></title> 
</head> 
<body>     
<form id="form1" runat="server">     
<div>             
 <asp:PlaceHolder ID="placeholder1" runat="server">        
          </asp:PlaceHolder>          


             
 <asp:Button ID="btn1" runat="server" onclick="btn1_Click" Text="Invia" />          
</div>    
 </form> 
</body> 
</html> 
Codice PHP:
using System;
 using System.Collections.Generic; 
using System.Linq;
 using System.Web; 
using System.Web.UI; 
using System.Web.UI.WebControls; 
using System.Web.UI.HtmlControls;  

namespace Forum {     

public partial class _Default : System.Web.UI.Page     
{         
RadioButtonList pippo = new RadioButtonList();         

 protected void Page_Load(object sender, EventArgs e)         
{             
for (int i = 0; i < 10; i++)            
 {                 
ListItem li = new ListItem(i.ToString(), i.ToString());                 
pippo.Items.Add(li);             
}             
 placeholder1.Controls.Add(pippo);         
}          

protected void btn1_Click(object sender, EventArgs e)         
{             
ListItem li = pippo.SelectedItem as ListItem;              
if (li != null)             
{                 
Response.Write(string.Format("{0} - {1}", li.Text, li.Value));            
 }         
}     
} 
} 

Ti consiglio un buon libro di asp.net.
Tra Asp e Asp.Net l'unica cosa in comune sono le iniziali del nome.
Sono due tecnologie completamente differenti.

In bocca al lupo