Use below code on your button click event.....its too simplestring serverUrl = "https://paypal.com/us/cgi-bin/webscr";string amount = "100";string shipping = "0";string baseUrl = HttpContext.Current.Request.Url.AbsoluteUri.Replace(HttpContext.Current.Request.Url.PathAndQuery, "") + HttpContext.Current.Request.ApplicationPath;if (!baseUrl.EndsWith("/"))baseUrl += "/";string cancelUrl = HttpUtility.UrlEncode(baseUrl + "OrderCompleted.aspx");//specify cancel urlstring notifyUrl = HttpUtility.UrlEncode(baseUrl + "Notify.aspx");//specify Notification urlstring returnUrl = HttpUtility.UrlEncode(baseUrl + "OrderCompleted.aspx?ID=1");//specify order completed urlstring business = "nikhil_1253111116_biz@librawebsolutions.com";string itemName = HttpUtility.UrlEncode("Order #100" );StringBuilder url = new StringBuilder();url.AppendFormat("{0}?cmd=_xclick&upload=1&rm=2&no_shipping=1&no_note=1¤cy_code={1}&business={2}&item_number={3}&custom={3}&item_name={4}&amount={5}&shipping={6}¬ify_url={7}&return={8}&cancel_return={9}",serverUrl, "USD", business, 1, itemName,amount, shipping, notifyUrl, returnUrl, cancelUrl);Response.Redirect(url.ToString(),false);that's it !
