微信公众号发起微信支付 c#

tenpay.dll：

MD5Util.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Security.Cryptography;

namespace tenpay
{
    public class MD5Util
    {
        public MD5Util()
        {
            //
            // TODO: 在此处添加构造函数逻辑
            //
        }

        /** 获取大写的MD5签名结果 */
        public static string GetMD5(string encypStr, string charset)
        {
            string retStr;
            MD5CryptoServiceProvider m5 = new MD5CryptoServiceProvider();

            //创建md5对象
            byte[] inputBye;
            byte[] outputBye;

            //使用GB2312编码方式把字符串转化为字节数组．
            try
            {
                inputBye = Encoding.GetEncoding(charset).GetBytes(encypStr);
            }
            catch (Exception ex)
            {
                inputBye = Encoding.GetEncoding("GB2312").GetBytes(encypStr);
            }
            outputBye = m5.ComputeHash(inputBye);

            retStr = System.BitConverter.ToString(outputBye);
            retStr = retStr.Replace("-", "").ToUpper();
            return retStr;
        }
    }
}

OrderDetail.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace tenpay
{
    /// <summary>
    /// 微信订单明细实体对象
    /// </summary>
    [Serializable]
    public class OrderDetail
    {
        /// <summary>
        /// 返回状态码，SUCCESS/FAIL 此字段是通信标识，非交易标识，交易是否成功需要查看trade_state来判断
        /// </summary>
        public string return_code = "";

        /// <summary>
        /// 返回信息返回信息，如非空，为错误原因 签名失败 参数格式校验错误
        /// </summary>
        public string return_msg = "";

        /// <summary>
        /// 公共号ID(微信分配的公众账号 ID)
        /// </summary>
        public string appid = "";

        /// <summary>
        /// 商户号(微信支付分配的商户号)
        /// </summary>
        public string mch_id = "";

        /// <summary>
        /// 随机字符串，不长于32位
        /// </summary>
        public string nonce_str = "";

        /// <summary>
        /// 签名
        /// </summary>
        public string sign = "";

        /// <summary>
        /// 业务结果,SUCCESS/FAIL
        /// </summary>
        public string result_code = "";

        /// <summary>
        /// 错误代码
        /// </summary>
        public string err_code = "";

        /// <summary>
        /// 错误代码描述
        /// </summary>
        public string err_code_des = "";

        /// <summary>
        /// 交易状态
        ///SUCCESS—支付成功
        ///REFUND—转入退款
        ///NOTPAY—未支付
        ///CLOSED—已关闭
        ///REVOKED—已撤销
        ///USERPAYING--用户支付中
        ///NOPAY--未支付(输入密码或确认支付超时) PAYERROR--支付失败(其他原因，如银行返回失败)
        /// </summary>
        public string trade_state = "";

        /// <summary>
        /// 微信支付分配的终端设备号
        /// </summary>
        public string device_info = "";

        /// <summary>
        /// 用户在商户appid下的唯一标识
        /// </summary>
        public string openid = "";
       
        /// <summary>
        /// 用户是否关注公众账号，Y-关注，N-未关注，仅在公众账号类型支付有效
        /// </summary>
        public string is_subscribe = "";

        /// <summary>
        /// 交易类型,JSAPI、NATIVE、MICROPAY、APP
        /// </summary>
        public string trade_type = "";

        /// <summary>
        /// 银行类型，采用字符串类型的银行标识
        /// </summary>
        public string bank_type = "";

        /// <summary>
        /// 订单总金额，单位为分
        /// </summary>
        public string total_fee = "";

        /// <summary>
        /// 现金券支付金额<=订单总金额，订单总金额-现金券金额为现金支付金额
        /// </summary>
        public string coupon_fee = "";

        /// <summary>
        /// 货币类型，符合ISO 4217标准的三位字母代码，默认人民币：CNY
        /// </summary>
        public string fee_type = "";

        /// <summary>
        /// 微信支付订单号
        /// </summary>
        public string transaction_id = "";

        /// <summary>
        /// 商户系统的订单号，与请求一致。
        /// </summary>
        public string out_trade_no = "";

        /// <summary>
        /// 商家数据包，原样返回
        /// </summary>
        public string attach = "";

        /// <summary>
        /// 支付完成时间，格式为yyyyMMddhhmmss，如2009年12月27日9点10分10秒表示为20091227091010。
        /// 时区为GMT+8 beijing。该时间取自微信支付服务器
        /// </summary>
        public string time_end = "";

    }
}

QueryOrder.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace tenpay
{
    /// <summary>
    /// 微信订单查询接口请求实体对象
    /// </summary>
    [Serializable]
    public class QueryOrder
    {
        /// <summary>
        /// 公共号ID(微信分配的公众账号 ID)
        /// </summary>
        public string appid = "";

        /// <summary>
        /// 商户号(微信支付分配的商户号)
        /// </summary>
        public string mch_id = "";

        /// <summary>
        /// 微信订单号，优先使用
        /// </summary>
        public string transaction_id = "";

        /// <summary>
        /// 商户系统内部订单号
        /// </summary>
        public string out_trade_no = "";

        /// <summary>
        /// 随机字符串，不长于 32 位
        /// </summary>
        public string nonce_str = "";

        /// <summary>
        /// 签名，参与签名参数：appid，mch_id，transaction_id，out_trade_no，nonce_str，key
        /// </summary>
        public string sign = "";
    }
}

UnifiedOrder.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace tenpay
{
    /// <summary>
    /// 微信统一接口请求实体对象
    /// </summary>
    [Serializable]
    public class UnifiedOrder
    {
        /// <summary>
        /// 公共号ID(微信分配的公众账号 ID)
        /// </summary>
        public string appid = "";
        /// <summary>
        /// 商户号(微信支付分配的商户号)
        /// </summary>
        public string mch_id = "";
        /// <summary>
        /// 微信支付分配的终端设备号
        /// </summary>
        public string device_info = "";
        /// <summary>
        /// 随机字符串，不长于 32 位
        /// </summary>
        public string nonce_str = "";
        /// <summary>
        /// 签名
        /// </summary>
        public string sign = "";
        /// <summary>
        /// 商品描述
        /// </summary>
        public string body = "";
        /// <summary>
        /// 附加数据，原样返回
        /// </summary>
        public string attach = "";
        /// <summary>
        /// 商户系统内部的订单号,32个字符内、可包含字母,确保在商户系统唯一,详细说明
        /// </summary>
        public string out_trade_no = "";
        /// <summary>
        /// 订单总金额，单位为分，不能带小数点
        /// </summary>
        public int total_fee = 0;
        /// <summary>
        /// 终端IP
        /// </summary>
        public string spbill_create_ip = "";
        /// <summary>
        /// 订 单 生 成 时 间 ， 格 式 为yyyyMMddHHmmss，如 2009 年12 月 25 日 9 点 10 分 10 秒表示为 20091225091010。时区为 GMT+8 beijing。该时间取自商户服务器
        /// </summary>
        public string time_start = "";
        /// <summary>
        /// 交易结束时间
        /// </summary>
        public string time_expire = "";
        /// <summary>
        /// 商品标记 商品标记，该字段不能随便填，不使用请填空，使用说明详见第 5 节
        /// </summary>
        public string goods_tag = "";
        /// <summary>
        /// 接收微信支付成功通知
        /// </summary>
        public string notify_url = "";
        /// <summary>
        /// JSAPI、NATIVE、APP
        /// </summary>
        public string trade_type = "";
        /// <summary>
        /// 用户标识 trade_type 为 JSAPI时，此参数必传
        /// </summary>
        public string openid = "";
        /// <summary>
        /// 只在 trade_type 为 NATIVE时需要填写。
        /// </summary>
        public string product_id = "";
    }
}

TenpayUtil.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml;

namespace tenpay
{
    public class TenpayUtil
    {
        /// <summary>
        /// 统一支付接口
        /// </summary>
        const string UnifiedPayUrl = "https://api.mch.weixin.qq.com/pay/unifiedorder";

        /// <summary>
        /// 网页授权接口
        /// </summary>
        const string access_tokenUrl = "https://api.weixin.qq.com/sns/oauth2/access_token";

        /// <summary>
        /// 微信订单查询接口
        /// </summary>
        const string OrderQueryUrl = "https://api.mch.weixin.qq.com/pay/orderquery";

        /// <summary>
        /// 随机串
        /// </summary>
        public static string getNoncestr()
        {
            Random random = new Random();
            return MD5Util.GetMD5(random.Next(1000).ToString(), "GBK").ToLower().Replace("s", "S");
        }

        /// <summary>
        /// 时间截，自1970年以来的秒数
        /// </summary>
        public static string getTimestamp()
        {
            TimeSpan ts = DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, 0);
            return Convert.ToInt64(ts.TotalSeconds).ToString();
        }

        /// <summary>
        /// 网页授权接口
        /// </summary>
        public static string getAccess_tokenUrl()
        {
            return access_tokenUrl;
        }

        /// <summary>
        /// 获取微信签名
        /// </summary>
        /// <param name="sParams"></param>
        /// <returns></returns>
        public string getsign(SortedDictionary<string, string> sParams, string key)
        {
            int i = 0;
            string sign = string.Empty;
            StringBuilder sb = new StringBuilder();
            foreach (KeyValuePair<string, string> temp in sParams)
            {
                if (temp.Value == "" || temp.Value == null || temp.Key.ToLower() == "sign")
                {
                    continue;
                }
                i++;
                sb.Append(temp.Key.Trim() + "=" + temp.Value.Trim() + "&");
            }
            sb.Append("key=" + key.Trim() + "");
            string signkey = sb.ToString();
            sign = MD5Util.GetMD5(signkey, "utf-8");


            return sign;
        }

        /// <summary>
        /// post数据到指定接口并返回数据
        /// </summary>
        public string PostXmlToUrl(string url, string postData)
        {
            string returnmsg = "";
            using (System.Net.WebClient wc = new System.Net.WebClient())
            {
                returnmsg = wc.UploadString(url, "POST", postData);
            }
            return returnmsg;
        }

        /// <summary>
        /// 获取prepay_id
        /// </summary>
        public string getPrepay_id(UnifiedOrder order, string key)
        {
            string prepay_id = "";
            string post_data = getUnifiedOrderXml(order, key);
            string request_data = PostXmlToUrl(UnifiedPayUrl, post_data);
            SortedDictionary<string, string> requestXML = GetInfoFromXml(request_data);
            foreach (KeyValuePair<string, string> k in requestXML)
            {
                if (k.Key == "prepay_id")
                {
                    prepay_id = k.Value;
                    break;
                }
            }
            return prepay_id;
        }

        /// <summary>
        /// 获取微信订单明细
        /// </summary>
        public OrderDetail getOrderDetail(QueryOrder queryorder, string key)
        {
            string post_data = getQueryOrderXml(queryorder, key);
            string request_data = PostXmlToUrl(OrderQueryUrl, post_data);
            OrderDetail orderdetail = new OrderDetail();
            SortedDictionary<string, string> requestXML = GetInfoFromXml(request_data);
            foreach (KeyValuePair<string, string> k in requestXML)
            {
                switch (k.Key)
                {
                    case "retuen_code":
                        orderdetail.result_code = k.Value;
                        break;
                    case "return_msg":
                        orderdetail.return_msg = k.Value;
                        break;
                    case "appid":
                        orderdetail.appid = k.Value;
                        break;
                    case "mch_id":
                        orderdetail.mch_id = k.Value;
                        break;
                    case "nonce_str":
                        orderdetail.nonce_str = k.Value;
                        break;
                    case "sign":
                        orderdetail.sign = k.Value;
                        break;
                    case "result_code":
                        orderdetail.result_code = k.Value;
                        break;
                    case "err_code":
                        orderdetail.err_code = k.Value;
                        break;
                    case "err_code_des":
                        orderdetail.err_code_des = k.Value;
                        break;
                    case "trade_state":
                        orderdetail.trade_state = k.Value;
                        break;
                    case "device_info":
                        orderdetail.device_info = k.Value;
                        break;
                    case "openid":
                        orderdetail.openid = k.Value;
                        break;
                    case "is_subscribe":
                        orderdetail.is_subscribe = k.Value;
                        break;
                    case "trade_type":
                        orderdetail.trade_type = k.Value;
                        break;
                    case "bank_type":
                        orderdetail.bank_type = k.Value;
                        break;
                    case "total_fee":
                        orderdetail.total_fee = k.Value;
                        break;
                    case "coupon_fee":
                        orderdetail.coupon_fee = k.Value;
                        break;
                    case "fee_type":
                        orderdetail.fee_type = k.Value;
                        break;
                    case "transaction_id":
                        orderdetail.transaction_id = k.Value;
                        break;
                    case "out_trade_no":
                        orderdetail.out_trade_no = k.Value;
                        break;
                    case "attach":
                        orderdetail.attach = k.Value;
                        break;
                    case "time_end":
                        orderdetail.time_end = k.Value;
                        break;
                    default:
                        break;
                }
            }
            return orderdetail;
        }

        /// <summary>
        /// 把XML数据转换为SortedDictionary<string, string>集合
        /// </summary>
        /// <param name="strxml"></param>
        /// <returns></returns>
        protected SortedDictionary<string, string> GetInfoFromXml(string xmlstring)
        {
            SortedDictionary<string, string> sParams = new SortedDictionary<string, string>();
            try
            {
                XmlDocument doc = new XmlDocument();
                doc.LoadXml(xmlstring);
                XmlElement root = doc.DocumentElement;
                int len = root.ChildNodes.Count;
                for (int i = 0; i < len; i++)
                {
                    string name = root.ChildNodes[i].Name;
                    if (!sParams.ContainsKey(name))
                    {
                        sParams.Add(name.Trim(), root.ChildNodes[i].InnerText.Trim());
                    }
                }
            }
            catch { }
            return sParams;
        }

        /// <summary>
        /// 微信统一下单接口xml参数整理
        /// </summary>
        /// <param name="order">微信支付参数实例</param>
        /// <param name="key">密钥</param>
        /// <returns></returns>
        protected string getUnifiedOrderXml(UnifiedOrder order, string key)
        {
            string return_string = string.Empty;
            SortedDictionary<string, string> sParams = new SortedDictionary<string, string>();
            sParams.Add("appid", order.appid);
            sParams.Add("attach", order.attach);
            sParams.Add("body", order.body);
            sParams.Add("device_info", order.device_info);
            sParams.Add("mch_id", order.mch_id);
            sParams.Add("nonce_str", order.nonce_str);
            sParams.Add("notify_url", order.notify_url);
            sParams.Add("openid", order.openid);
            sParams.Add("out_trade_no", order.out_trade_no);
            sParams.Add("spbill_create_ip", order.spbill_create_ip);
            sParams.Add("total_fee", order.total_fee.ToString());
            sParams.Add("trade_type", order.trade_type);
            order.sign = getsign(sParams, key);
            sParams.Add("sign", order.sign);

            //拼接成XML请求数据
            StringBuilder sbPay = new StringBuilder();
            foreach (KeyValuePair<string, string> k in sParams)
            {
                if (k.Key == "attach" || k.Key == "body" || k.Key == "sign")
                {
                    sbPay.Append("<" + k.Key + "><![CDATA[" + k.Value + "]]></" + k.Key + ">");
                }
                else
                {
                    sbPay.Append("<" + k.Key + ">" + k.Value + "</" + k.Key + ">");
                }
            }
            return_string = string.Format("<xml>{0}</xml>", sbPay.ToString());
            byte[] byteArray = Encoding.UTF8.GetBytes(return_string);
            return_string = Encoding.GetEncoding("GBK").GetString(byteArray);
            return return_string;
            
        }

        /// <summary>
        /// 微信订单查询接口XML参数整理
        /// </summary>
        /// <param name="queryorder">微信订单查询参数实例</param>
        /// <param name="key">密钥</param>
        /// <returns></returns>
        protected string getQueryOrderXml(QueryOrder queryorder, string key)
        {
            string return_string = string.Empty;
            SortedDictionary<string, string> sParams = new SortedDictionary<string, string>();
            sParams.Add("appid", queryorder.appid);
            sParams.Add("mch_id", queryorder.mch_id);
            sParams.Add("transaction_id", queryorder.transaction_id);
            sParams.Add("out_trade_no", queryorder.out_trade_no);
            sParams.Add("nonce_str", queryorder.nonce_str);
            queryorder.sign = getsign(sParams, key);
            sParams.Add("sign", queryorder.sign);

            //拼接成XML请求数据
            StringBuilder sbPay = new StringBuilder();
            foreach (KeyValuePair<string, string> k in sParams)
            {
                if (k.Key == "attach" || k.Key == "body" || k.Key == "sign")
                {
                    sbPay.Append("<" + k.Key + "><![CDATA[" + k.Value + "]]></" + k.Key + ">");
                }
                else
                {
                    sbPay.Append("<" + k.Key + ">" + k.Value + "</" + k.Key + ">");
                }
            }
            return_string = string.Format("<xml>{0}</xml>", sbPay.ToString().TrimEnd(','));
            return return_string;
        }
    }
}

 看官网例子：

function onBridgeReady(){
   WeixinJSBridge.invoke(
       'getBrandWCPayRequest', {
           "appId" : "wx2421b1c4370ec43b",     //公众号名称，由商户传入     
           "timeStamp":" 1395712654",         //时间戳，自1970年以来的秒数     
           "nonceStr" : "e61463f8efa94090b1f366cccfbbb444", //随机串     
           "package" : "prepay_id=u802345jgfjsdfgsdg888",     
           "signType" : "MD5",         //微信签名方式:     
           "paySign" : "70EA570631E4BB79628FBCA90534C63FF7FADD89" //微信签名 
       },
       function(res){     
           if(res.err_msg == "get_brand_wcpay_request:ok" ) {}     // 使用以上方式判断前端返回,微信团队郑重提示：res.err_msg将在用户支付成功后返回    ok，但并不保证它绝对可靠。 
       }
   ); 
}
if (typeof WeixinJSBridge == "undefined"){
   if( document.addEventListener ){
       document.addEventListener('WeixinJSBridgeReady', onBridgeReady, false);
   }else if (document.attachEvent){
       document.attachEvent('WeixinJSBridgeReady', onBridgeReady); 
       document.attachEvent('onWeixinJSBridgeReady', onBridgeReady);
   }
}else{
   onBridgeReady();
} 

主要是prepay_id和paySign的获取。类库tenpay.dll的作用就是获取这两个东西的。

大致流程：获取公众号的code——》获取预定单号的openid——》获取prepay_id。

1.根据自己的业务逻辑生成内部订单

    protected void btnPay_Click(object sender, EventArgs e)
    {
        if (Fetch.GetUserCookie() == null)
        {
            Response.Redirect("/App/Login.aspx?url=/App/indexPay.aspx");
            return;
        }

        int salePrice = Utility.StrToInt(OrderAmount, 0);
        OnLineOrder onlineOrder = new OnLineOrder();
        onlineOrder.ShareID = 13;
        onlineOrder.OrderID = PayHelper.GetOrderIDByPrefix("WX");

        #region 订单处理

        if (Fetch.GetUserCookie() == null)
        {
            onlineOrder.OperUserID = 0;
        }
        else
        {
            onlineOrder.OperUserID = Fetch.GetUserCookie().UserID;
        }
        onlineOrder.Accounts = Fetch.GetUserCookie().Accounts;
        onlineOrder.CardTotal = 1;
        onlineOrder.CardTypeID = salePrice / 10; //< 30 ? 1 : salePrice < 60 ? 2 : salePrice < 120 ? 3 : 4;
        onlineOrder.OrderAmount = salePrice;
        onlineOrder.IPAddress = GameRequest.GetUserIP();

        //生成订单
        Message umsg = treasureFacade.RequestOrder(onlineOrder);
        if (!umsg.Success)
        {
            RenderAlertInfo(true, umsg.Content, 2);
            return;
        }
        #endregion

        //发起微信支付

        Response.Redirect("https://open.weixin.qq.com/connect/oauth2/authorize?appid=你的公众号appid&redirect_uri=http://你的网站/App/Pay/PayOrder.aspx?showwxpaytitle=1&response_type=code&scope=snsapi_base&state=" + OrderAmount + "_" + onlineOrder.OrderID + "#wechat_redirect");

    }

2.进入公众号配置网页授权获取用户基本信息

这样配置后就可以调用微信的接口获取到公众号的code

Response.Redirect("https://open.weixin.qq.com/connect/oauth2/authorize?appid=你的公众号appid&redirect_uri=http://你的网站/App/Pay/PayOrder.aspx?showwxpaytitle=1&response_type=code&scope=snsapi_base&state=" + OrderAmount + "_" + onlineOrder.OrderID + "#wechat_redirect");

访问https://open.weixin.qq.com/connect/oauth2/authorize接口，成功后会跳转到设置的redirect_uri页面，其中会包含code参数，接下来就到redirect_uri页面（我这里就是PayOrder.aspx了）简单的获取code参数：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using Game.Utils;
using System.Web.Script.Serialization;
using tenpay;
using System.Configuration;
using System.Text;

public partial class App_Pay_PayOrder : System.Web.UI.Page
{
    protected string code = GameRequest.GetQueryString("code");
    protected string state = GameRequest.GetQueryString("state");
    protected string OrderAmount = "";
    protected string OrderID = "";
    protected string OrderTime = "";
    protected string OrderGive = "";
    protected string ImagePath = "";
    protected string appId = "";
    protected string timeStamp = "";
    protected string nonceStr = "";
    protected string prepay_id = "";
    protected string paySign = "";

    protected void Page_Load(object sender, EventArgs e)
    {
    LoadOrder();
    }

    private void LoadOrder()
    {
        string[] values = state.Split('_');
        if (values.Length == 2)
        {
            OrderAmount = values[0];
            OrderID = values[1];
        }
        OrderTime = (new DataControl()).SelectValue("select ApplayDate from OnLineOrder where OrderId='" + OrderID + "'", "DBTreasure", "").ToString();
        ImagePath = (new DataControl()).SelectValue("select ImagePath from CartTypeImage where CardTypeId=" + OrderAmount, "DBTreasure", "").ToString();
    }

    public struct authorization
    {
        public string access_token { get; set; }  //属性的名字，必须与json格式字符串中的"key"值一样。
        public string expires_in { get; set; }
        public string refresh_token { get; set; }
        public string openid { get; set; }
        public string scope { get; set; }
    }

    protected void btnPay_Click(object sender, EventArgs e)
    {
        try
        {
            TenpayUtil tenpay = new TenpayUtil();
            string paySignKey = ConfigurationManager.AppSettings["paySignKey"].ToString();
            string AppSecret = ConfigurationManager.AppSettings["AppSecret"].ToString();
            string mch_id = ConfigurationManager.AppSettings["mch_id"].ToString();
            appId = ConfigurationManager.AppSettings["AppId"].ToString();

            string post_data = "appid=" + appId + "&secret=" + AppSecret + "&code=" + code + "&grant_type=authorization_code";
            string requestData = tenpay.PostXmlToUrl(TenpayUtil.getAccess_tokenUrl(), post_data);

            JavaScriptSerializer js = new JavaScriptSerializer();   //实例化一个能够序列化数据的类
            authorization auth = js.Deserialize<authorization>(requestData);    //将json数据转化为对象类型并赋值给auth


            UnifiedOrder order = new UnifiedOrder();
            order.appid = appId;
            order.attach = "vinson";
            order.body = OrderAmount + "拍币";
            order.device_info = "";
            order.mch_id = mch_id;
            order.nonce_str = TenpayUtil.getNoncestr();
            order.notify_url = "http://你的网站/App/Shop/pay.aspx";
            order.openid = auth.openid;
            order.out_trade_no = OrderID;
            order.trade_type = "JSAPI";
            order.spbill_create_ip = Page.Request.UserHostAddress;
            order.total_fee = int.Parse(OrderAmount) * 100;
            //order.total_fee = 1;

            prepay_id = tenpay.getPrepay_id(order, paySignKey);

            timeStamp = TenpayUtil.getTimestamp();
            nonceStr = TenpayUtil.getNoncestr();

            SortedDictionary<string, string> sParams = new SortedDictionary<string, string>();
            sParams.Add("appId", appId);
            sParams.Add("timeStamp", timeStamp);
            sParams.Add("nonceStr", nonceStr);
            sParams.Add("package", "prepay_id=" + prepay_id);
            sParams.Add("signType", "MD5");
            paySign = tenpay.getsign(sParams, paySignKey);

        }
        catch (Exception ex)
        {
            Response.Write(ex.ToString());
            return;
        }

        Response.Redirect("http://你的网站/App/Pay/pay.aspx?showwxpaytitle=1&appId=" + appId + "&timeStamp=" + timeStamp + "&nonceStr=" + nonceStr + "&prepay_id=" + prepay_id + "&signType=MD5&paySign=" + paySign + "&OrderID=" + OrderID);

    }
}

上面一句

protected string code = GameRequest.GetQueryString("code");

就获取到了传过来的code参数。

然后调用网页授权接口https://api.weixin.qq.com/sns/oauth2/access_token 获取openid

这个接口返回的数据是json类型的，使用JavaScriptSerializer类和结构体把openid取出：

    public struct authorization
    {
        public string access_token { get; set; }  //属性的名字，必须与json格式字符串中的"key"值一样。
        public string expires_in { get; set; }
        public string refresh_token { get; set; }
        public string openid { get; set; }
        public string scope { get; set; }
    }

            TenpayUtil tenpay = new TenpayUtil();
            string paySignKey = ConfigurationManager.AppSettings["paySignKey"].ToString();
            string AppSecret = ConfigurationManager.AppSettings["AppSecret"].ToString();
            string mch_id = ConfigurationManager.AppSettings["mch_id"].ToString();
            appId = ConfigurationManager.AppSettings["AppId"].ToString();

            string post_data = "appid=" + appId + "&secret=" + AppSecret + "&code=" + code + "&grant_type=authorization_code";
            string requestData = tenpay.PostXmlToUrl(TenpayUtil.getAccess_tokenUrl(), post_data);

            JavaScriptSerializer js = new JavaScriptSerializer();   //实例化一个能够序列化数据的类
            authorization auth = js.Deserialize<authorization>(requestData);    //将json数据转化为对象类型并赋值给auth

AppId和AppSecret是公众号里面给的，mch_id是通过微信支付申请后微信发邮件给的，paySignKey是自己设置的证书密阴

TenpayUtil.getAccess_tokenUrl()="https://api.weixin.qq.com/sns/oauth2/access_token"

这样转化后就可以得到openid

order.openid = auth.openid;

终于到重头戏获取prepay_id了

            UnifiedOrder order = new UnifiedOrder();
            order.appid = appId;
            order.attach = "vinson";
            order.body = OrderAmount + "拍币";
            order.device_info = "";
            order.mch_id = mch_id;
            order.nonce_str = TenpayUtil.getNoncestr();
            order.notify_url = "http://你的网站/App/Shop/pay.aspx";
            order.openid = auth.openid;
            order.out_trade_no = OrderID;
            order.trade_type = "JSAPI";
            order.spbill_create_ip = Page.Request.UserHostAddress;
            order.total_fee = int.Parse(OrderAmount) * 100;
            //order.total_fee = 1;

            prepay_id = tenpay.getPrepay_id(order, paySignKey);

对象类型UnifiedOrder方便把多个参数融合一个对象中，看看tenpay.getPrepay_id(order, paySignKey)方法：

        /// <summary>
        /// 获取prepay_id
        /// </summary>
        public string getPrepay_id(UnifiedOrder order, string key)
        {
            string prepay_id = "";
            string post_data = getUnifiedOrderXml(order, key);
            string request_data = PostXmlToUrl(UnifiedPayUrl, post_data);
            SortedDictionary<string, string> requestXML = GetInfoFromXml(request_data);
            foreach (KeyValuePair<string, string> k in requestXML)
            {
                if (k.Key == "prepay_id")
                {
                    prepay_id = k.Value;
                    break;
                }
            }
            return prepay_id;
        }

接口UnifiedPayUrl="https://api.mch.weixin.qq.com/pay/unifiedorder"

这个接口的参数是xml格式的，返回来的数据也是xml格式的

        /// <summary>
        /// 微信统一下单接口xml参数整理
        /// </summary>
        /// <param name="order">微信支付参数实例</param>
        /// <param name="key">密钥</param>
        /// <returns></returns>
        protected string getUnifiedOrderXml(UnifiedOrder order, string key)
        {
            string return_string = string.Empty;
            SortedDictionary<string, string> sParams = new SortedDictionary<string, string>();
            sParams.Add("appid", order.appid);
            sParams.Add("attach", order.attach);
            sParams.Add("body", order.body);
            sParams.Add("device_info", order.device_info);
            sParams.Add("mch_id", order.mch_id);
            sParams.Add("nonce_str", order.nonce_str);
            sParams.Add("notify_url", order.notify_url);
            sParams.Add("openid", order.openid);
            sParams.Add("out_trade_no", order.out_trade_no);
            sParams.Add("spbill_create_ip", order.spbill_create_ip);
            sParams.Add("total_fee", order.total_fee.ToString());
            sParams.Add("trade_type", order.trade_type);
            order.sign = getsign(sParams, key);
            sParams.Add("sign", order.sign);

            //拼接成XML请求数据
            StringBuilder sbPay = new StringBuilder();
            foreach (KeyValuePair<string, string> k in sParams)
            {
                if (k.Key == "attach" || k.Key == "body" || k.Key == "sign")
                {
                    sbPay.Append("<" + k.Key + "><![CDATA[" + k.Value + "]]></" + k.Key + ">");
                }
                else
                {
                    sbPay.Append("<" + k.Key + ">" + k.Value + "</" + k.Key + ">");
                }
            }
            return_string = string.Format("<xml>{0}</xml>", sbPay.ToString());
            byte[] byteArray = Encoding.UTF8.GetBytes(return_string);
            return_string = Encoding.GetEncoding("GBK").GetString(byteArray);
            return return_string;
            
        }

所有参数准备完毕，就剩下最后的微信签名paySign了：

            prepay_id = tenpay.getPrepay_id(order, paySignKey);

            timeStamp = TenpayUtil.getTimestamp();
            nonceStr = TenpayUtil.getNoncestr();

            SortedDictionary<string, string> sParams = new SortedDictionary<string, string>();
            sParams.Add("appId", appId);
            sParams.Add("timeStamp", timeStamp);
            sParams.Add("nonceStr", nonceStr);
            sParams.Add("package", "prepay_id=" + prepay_id);
            sParams.Add("signType", "MD5");
            paySign = tenpay.getsign(sParams, paySignKey);

这里要注意了：appId这些参数的大小写一定要和js那边的参数大小写一致！稍微有所不同都会提示“商户签名错误”。

<script type="text/javascript">
    var appId = "<%=appId %>";
    var timeStamp = "<%=timeStamp %>";
    var nonceStr = "<%=nonceStr %>";
    var prepay_id = "<%=prepay_id %>";
    var paySign = "<%=paySign %>";
    var OrderID="<%=OrderID %>";
    //alert("appId:" + appId + ",timeStamp:" + timeStamp + ",nonceStr:" + nonceStr + ",prepay_id:" + prepay_id + ",paySign:" + paySign);
    //return;
    function onBridgeReady() {
        WeixinJSBridge.invoke(
       'getBrandWCPayRequest', {
           "appId": appId,     //公众号名称，由商户传入     
           "timeStamp": timeStamp,         //时间戳，自1970年以来的秒数     
           "nonceStr": nonceStr, //随机串     
           "package": "prepay_id=" + prepay_id,
           "signType": "MD5",         //微信签名方式:     
           "paySign": paySign //微信签名 
       },
       function (res) {
           if (res.err_msg == "get_brand_wcpay_request:ok") {
               $(function () {
                   $.ajax({
                       contentType: "application/json",
                       url: "/WS/vinson.asmx/payWeiXin",
                       data: "{OrderID:'" + OrderID + "'}",
                       type: "POST",
                       dataType: "json",
                       success: function (json) {
                           json = eval("(" + json.d + ")");
                           if (json.success == "success") {
                               $("#tip").text("支付成功，正在跳转......");
                               window.location = "http://你的网站/App/Shop/successful.aspx";
                           }
                           else {
                               $("#tip").text(json.msg);
                               alert(json.msg);
                               window.location = "http://你的网站/App/indexPay.aspx";
                           }
                       },
                       error: function (err, ex) {
                           alert(err.responseText);
                       }
                   });
               })
           }     // 使用以上方式判断前端返回,微信团队郑重提示：res.err_msg将在用户支付成功后返回    ok，但并不保证它绝对可靠。 
           else {
               alert("交易取消");
               window.location="http://www.你的网站.cn/App/indexPay.aspx";
           }
       }
   );
    }
    if (typeof WeixinJSBridge == "undefined") {
        if (document.addEventListener) {
            document.addEventListener('WeixinJSBridgeReady', onBridgeReady, false);
        } else if (document.attachEvent) {
            document.attachEvent('WeixinJSBridgeReady', onBridgeReady);
            document.attachEvent('onWeixinJSBridgeReady', onBridgeReady);
        }
    } else {
        onBridgeReady();
    } 
</script>

要发起微信支付，还要到公众号设置支付授权目录：

一切准备就绪，就可以真正的发起微信支付了：