<FORM ACTION="http://localhost/shop/cybercrd.cgi"
 METHOD="POST">
<INPUT TYPE="HIDDEN" NAME="OrderID" VALUE="279">
<INPUT TYPE="HIDDEN" NAME="PaymentDetails"VALUE="оплата заказа 87687234">
<INPUT TYPE="HIDDEN" NAME="Amount" VALUE="3.00">
<INPUT TYPE="HIDDEN" NAME="Currency" VALUE="2">
<INPUT TYPE="HIDDEN" NAME="FirstName" VALUE="Иван">
<INPUT TYPE="HIDDEN" NAME="MiddleName" VALUE="Иванович">
<INPUT TYPE="HIDDEN" NAME="LastName" VALUE="Иванов">
<INPUT TYPE="HIDDEN" NAME="Email" VALUE="iii@ivanov.ru">
<INPUT TYPE="SUBMIT" NAME="Submit" VALUE="Оплатить">
</FORM>

HttpWebResponse result = null;	
HttpWebRequest req =(HttpWebRequest)WebRequest.Create("http://localhost/shop/cybercrd.cgi");
req.Method = "POST";
req.ContentType = "application/x-www-form-urlencoded";
byte[] SomeBytes = null;
string FormParams  = "OrderID=459&Amount=400&Currency=RUR&PaymentDetails=оплата заказа #10160156&Email=support@cyberplat.com&;FirstName=cyberplat&LastName=support&MiddleName=none&Phone=745-4060&Address=Moscow, Kutuzovsky pr. 12&Language=ru&return_url=http://localhost/shop/result.cgi"; 
ASCIIEncoding encode=new ASCIIEncoding();
SomeBytes = encode.GetBytes(FormParams);
req.ContentLength = SomeBytes.Length;		
Stream newStream = req.GetRequestStream();
newStream.Write(SomeBytes,  0 , SomeBytes.Length);
newStream.Close();
result = (HttpWebResponse) req.GetResponse();