using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Security.Cryptography;
using System.Text;
using System.Web;

namespace MZ.Common
{
    /// <summary>
    /// 支付宝即时到帐交易
    /// </summary>
    public class AlipayHelper
    {
        private string _partner;
        private string _key;
        private string _seller_email;
        private string _httpurl;
        private string __input_charset;
        private string _sign_type;
        private string _payment_type;

        /// <summary>
        /// 构造函数
        /// </summary>
        public AlipayHelper()
        {
            _partner = "2088000000000000";
            _key = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx";
            _seller_email = "dnawo@alipay.com";
            _httpurl = "https://www.alipay.com/cooperate/gateway.do?";
            __input_charset = "utf-8";
            _sign_type = "MD5";
            _payment_type = "1";            
        }

        /// <summary>
        /// 合作者身份ID(PID),支付宝网站获取
        /// </summary>
        public string Partner
        {
            get { return _partner; }
            set { _partner = value; }
        }

        /// <summary>
        /// MD5私钥(Key),支付宝网站获取
        /// </summary>
        public string Key
        {
            get { return _key; }
            set { _key = value; }
        }

        /// <summary>
        /// 卖家支付宝帐号
        /// </summary>
        public string SellerEmail
        {
            get { return _seller_email; }
            set { _seller_email = value; }
        }

        /// <summary>
        /// 支付请求、验证请求接口
        /// </summary>
        public string HttpUrl
        {
            get { return _httpurl; }
            set { _httpurl = value; }
        }

        /// <summary>
        /// 参数编码字符集：utf-8、gb2312、gbk
        /// </summary>
        public string InputCharset
        {
            get { return __input_charset; }
            set { __input_charset = value; }
        }

        /// <summary>
        /// 签名方式：DSA、RSA、MD5
        /// </summary>
        public string SignType
        {
            get { return _sign_type; }
            set { _sign_type = value; }
        }

        /// <summary>
        /// 收款类型：1商品购买、4捐赠
        /// </summary>
        public string PaymentType
        {
            get { return _payment_type; }
            set { _payment_type = value; }
        }

        /// <summary>
        /// 生成签名
        /// </summary>
        /// <param name="parameters"></param>
        private string Signature(SortedList<string, string> parameters)
        {
            StringBuilder sb = new StringBuilder();
            foreach (KeyValuePair<string, string> item in parameters)
            {
                if (item.Key != "sign" && item.Key != "sign_type")
                {
                    sb.Append(string.Format("{0}={1}&", item.Key.ToLower(), item.Value));
                }
            }
            string str = sb.ToString().TrimEnd('&') + Key;
            MD5CryptoServiceProvider MD5 = new MD5CryptoServiceProvider();
            return BitConverter.ToString(MD5.ComputeHash(Encoding.GetEncoding(InputCharset).GetBytes(str))).Replace("-", "").ToLower();

        }

        /// <summary>
        /// 生成请求URL
        /// </summary>
        /// <param name="parameters"></param>
        /// <returns></returns>
        private string CreateURL(SortedList<string, string> parameters)
        {
            StringBuilder sb = new StringBuilder();
            foreach (KeyValuePair<string, string> item in parameters)
            {
                sb.Append(string.Format("{0}={1}&", item.Key.ToLower(), HttpUtility.UrlEncode(item.Value, Encoding.GetEncoding(InputCharset))));
            }
            return HttpUrl + sb.ToString().TrimEnd('&');
        }

        /// <summary>
        /// HTPP请求
        /// </summary>
        /// <param name="url"></param>
        /// <returns></returns>
        private string HttpGet(string url)
        {
            try
            {
                Encoding encoding = Encoding.GetEncoding(InputCharset);
                Uri uri = new Uri(url);
                WebRequest webRequest = WebRequest.Create(uri);
                webRequest.ContentType = "application/x-www-form-urlencoded";
                webRequest.Method = "GET";
                WebResponse webResponse = webRequest.GetResponse();
                using (StreamReader reader = new StreamReader(webResponse.GetResponseStream(), encoding))
                {
                    return reader.ReadToEnd();
                }
            }
            catch
            {
                return "";
            }
        }

        /// <summary>
        /// 支付
        /// </summary>
        /// <param name="subject">商品名称</param>
        /// <param name="total_fee">交易金额,精确到两位小数</param>
        /// <param name="out_trade_no">商户网站订单号</param>
        /// <param name="return_url">同步通知页面</param>
        /// <returns></returns>
        public string Pay(string subject, string total_fee, string out_trade_no, string return_url)
        {
            SortedList<string, string> parameters = new SortedList<string, string>();
            parameters.Add("service", "create_direct_pay_by_user"); //接口名称
            parameters.Add("partner", Partner);
            parameters.Add("_input_charset", InputCharset);            
            parameters.Add("seller_email", SellerEmail);
            parameters.Add("payment_type", PaymentType);
            parameters.Add("sign_type", SignType);
            parameters.Add("subject", subject);            
            parameters.Add("total_fee", total_fee);
            parameters.Add("out_trade_no", out_trade_no);
            parameters.Add("return_url", return_url);            
            parameters.Add("sign", Signature(parameters));

            return CreateURL(parameters);
        }

        /// <summary>
        /// 验证交易状态
        /// </summary>
        /// <param name="trade_status">交易状态</param>
        /// <param name="notify_id">通知校验ID</param>
        /// <returns></returns>
        public bool NotifyVerify(string trade_status, string notify_id)
        {
            bool result = false;
            
            if (trade_status.ToUpper() == "TRADE_FINISHED" || trade_status.ToUpper() == "TRADE_SUCCESS")
            {
                SortedList<string, string> parameters = new SortedList<string, string>();
                parameters.Add("service", "notify_verify"); //接口名称
                parameters.Add("partner", Partner);
                parameters.Add("notify_id", notify_id);

                //判断是否来源来支付宝,务必在支付宝同步1分钟内验证,否则结果都为false
                if (HttpGet(CreateURL(parameters)).ToLower().IndexOf("true") != -1)
                    result = true;
            }

            return result;
        }
    }
}

<%@ 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>支付宝即时到帐交易接口示例-Mzwu.Com</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <asp:Button ID="btnPay" runat="server" onclick="btnPay_Click" Text="开始支付" />
        <br />
        <asp:Label ID="lblReturnMsg" runat="server" Text="lblReturnMsg"></asp:Label>
    </div>
    </form>
</body>
</html>

using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Security.Cryptography;
using System.Text;
using System.Web;
using MZ.Common;

public partial class _Default : System.Web.UI.Page
{
    /// <summary>
    /// 页面加载
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    protected void Page_Load(object sender, EventArgs e)
    {
        //支付宝同步状态
        if (!Page.IsPostBack && Request.QueryString["trade_status"] != null)
        {
            Verify();
        }
    }

    /// <summary>
    /// 1.开始支付
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    protected void btnPay_Click(object sender, EventArgs e)
    {
        AlipayHelper alipay = new AlipayHelper();
        string url = alipay.Pay("竹炭颈椎枕", "0.01", DateTime.Now.ToString("yyyyMMddHHmmss"), "http://127.0.0.1/");
        Response.Redirect(url);
    }

    /// <summary>
    /// 2.支付结果
    /// </summary>
    protected void Verify()
    {
        AlipayHelper alipay = new AlipayHelper();
        bool status = alipay.NotifyVerify(Request.QueryString["trade_status"], Request.QueryString["notify_id"]);

        if (status)
            lblReturnMsg.Text = "订单(" + Request.QueryString["out_trade_no"] + ")支付成功！";
        else
            lblReturnMsg.Text = "订单(" + Request.QueryString["out_trade_no"] + ")支付失败！";

    }
}