Good Dal All

i have this aspx page

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

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "">

<html xmlns="">
<head runat="server">
    <form runat="server" method="post"  action="" >
    <asp:HiddenField ID="p1" Value="4635" runat="server" />
    <asp:HiddenField ID="p2" Value="2" runat="server" />
    <asp:HiddenField ID="p3" Value="Some Goods" runat="server" />
    <asp:HiddenField ID="p4" Value="5.00" runat="server" />
    <asp:Button ID="btnSubmit" runat="server" Text="Pay by Credit Card" 
what happens here is that on the Client side when someone clicks the Button it will do the payment and redirect to the page, i want to do this one the server side. i tried this

  protected void btnSubmit_Click1(object sender, EventArgs e)

        string P1 =  p1.Value;
        string P2 = p2.Value;

        string P3 = p3.Value;

        String URl = "" + P1 + "&p2=" + P2 + "&p3=" + P3;
        WebClient svc = new WebClient();
        svc.UploadStringAsync(new Uri(""), "Post", "AT");
        svc.UploadStringCompleted += new UploadStringCompletedEventHandler(svc_UploadStringCompleted);
    void svc_UploadStringCompleted(object sender, UploadStringCompletedEventArgs e)
        String estr = e.Result;
You can test using that URL