微信小程序支付服务端.net core实现，简单直接

做小程序的支付时，在翻阅了大量的别人分享的代码后，感觉写的简直就是一堆垃圾，不敢苟同，要是代码都那么写，维护性简直了，于是才有了这篇文章。

首先流程是很清楚的，就是先统一下单拼一个xml，然后把有值的参数排序后做计算一个签名，把签名也写到xml中，提交给微信，返回发起支付需要的参数，紧接着进行二次签名，将结果返回给小程序，小程序去调微信api发起支付

1，将需要拼接程xml的参数都写到一个类里边

 [Serializable]
    [XmlRoot(ElementName = "xml", Namespace = "",IsNullable =true,DataType ="")]
    public class WxUnifiedOrder
    {
        [XmlElement(ElementName = "appid")]
        public string AppId { get; set; }
        [XmlElement(ElementName = "mch_id")]
        public string Mch_Id { get; set; }
        [XmlElement(ElementName = "device_info")]
        public string Device_Info { get; set; }
        [XmlElement(ElementName = "nonce_str")]
        public string Nonce_Str { get; set; }

        [XmlElement(ElementName = "sign")]
        public string Sign { get; set; }
        /// <summary>
        /// 商品描述
        /// </summary>
        [XmlElement(ElementName = "body")]
        public string Body { get; set; }
        /// <summary>
        /// 商户订单号
        /// </summary>
        [XmlElement(ElementName = "out_trade_no")]
        public string Out_Trade_No { get; set; }
        /// <summary>
        /// 订单金额
        /// </summary>
        [XmlElement(ElementName = "total_fee")]
        public int Total_Fee { get; set; }
        /// <summary>
        /// 终端IP
        /// </summary>
        [XmlElement(ElementName = "spbill_create_ip")]
        public string Spbill_Create_Ip { get; set; }
        /// <summary>
        /// 通知地址
        /// </summary>
        [XmlElement(ElementName = "notify_url")]
        public string Notify_Url { get; set; }
        /// <summary>
        /// 交易类型
        /// </summary>
        [XmlElement(ElementName = "trade_type")]
        public string Trade_Type { get; set; }

        [XmlElement(ElementName = "openid")]
        public string OpenId { get; set; }

加上特性，标明最终生成xml的文档结构。

2，写个xml简单的操作类，就是个序列化和反序列化的过程

 public static class XMLOption
    {
        public static string ToXml<T>(this T obj, Encoding encoding)
        {
            string result = string.Empty;
            try
            {
                using (MemoryStream memoryStream = new MemoryStream())
                {
                    XmlSerializer xmlSerializer = new XmlSerializer(obj.GetType());
                    //序列化对象
                    XmlSerializerNamespaces namespaes = new XmlSerializerNamespaces();
                    namespaes.Add("", "");
                    XmlTextWriter xmlTextWriter = new XmlTextWriter(memoryStream, encoding);
                    xmlTextWriter.Formatting = System.Xml.Formatting.None;
                    xmlSerializer.Serialize(xmlTextWriter, obj, namespaes);
                    xmlTextWriter.Flush();
                    xmlTextWriter.Close();
                    result = encoding.GetString(memoryStream.ToArray());
                }
            }
            catch (Exception ex)
            {

            }
            return result;
        }

        public static T ToXmlObject<T>(this string str, Encoding encoding)
        {
            try
            {
                using (MemoryStream memoryStream = new MemoryStream())
                {
                   
                    var buffer = encoding.GetBytes(str);
                    memoryStream.Write(buffer, 0, buffer.Length);
                    memoryStream.Position = 0;
                    XmlSerializer xmlSerializer = new XmlSerializer(typeof(T));
                    var result = xmlSerializer.Deserialize(memoryStream);
                    return (T)result;
                }
            }
            catch (Exception ex)
            {
                return default;
            }
        }
    }

3.一个模拟post请求的公用方法

 /// <summary>  
        /// 模拟POST提交  
        /// </summary>  
        /// <param name="url">请求地址</param>  
        /// <param name="xmlParam">xml参数</param>  
        /// <returns>返回结果</returns>  
        public string PostHttpResponse(string url, string xmlParam)
        {
            HttpWebRequest myHttpWebRequest = (HttpWebRequest)HttpWebRequest.Create(url);
            myHttpWebRequest.Method = "POST";
            myHttpWebRequest.ContentType = "application/x-www-form-urlencoded;charset=utf-8";

            // Encode the data  
            byte[] encodedBytes = Encoding.UTF8.GetBytes(xmlParam);
            myHttpWebRequest.ContentLength = encodedBytes.Length;

            // Write encoded data into request stream  
            Stream requestStream = myHttpWebRequest.GetRequestStream();
            requestStream.Write(encodedBytes, 0, encodedBytes.Length);
            requestStream.Close();

            HttpWebResponse result;

            try
            {
                result = (HttpWebResponse)myHttpWebRequest.GetResponse();
            }
            catch
            {
                return string.Empty;
            }

            if (result.StatusCode == HttpStatusCode.OK)
            {
                using (Stream mystream = result.GetResponseStream())
                {
                    using (StreamReader reader = new StreamReader(mystream))
                    {
                        return reader.ReadToEnd();
                    }
                }
            }
            return null;
        }

4.再来一个扩展方法，计算string字符串的md5值

 /// <summary>
        /// 对字符串进行MD5加密
        /// </summary>
        /// <param name="strIN">需要加密的字符串</param>
        /// <returns>密文</returns>
        public static string MD5(this string source)
        {
            if (source == null)
            {
                return null;
            }
            using (MD5 md5 = System.Security.Cryptography.MD5.Create())
            {
                byte[] result = md5.ComputeHash(Encoding.UTF8.GetBytes(source));
                string strResult = BitConverter.ToString(result);
                return strResult.Replace("-", "");
            }
        }

5.填充需要提交的信息，并计算签名

 var wxUnifiedOrder = new WxUnifiedOrder()
            {
                AppId = wxsetting.Appid,
                Body = product.Name,
                Device_Info = "WEB",
                Mch_Id = wxsetting.Mch_id,
                Nonce_Str = Guid.NewGuid().ToString().Replace("-", "").ToUpper(),
                Notify_Url = _configuration["WechatPaied:Notify_Url"],
                Out_Trade_No = orderinfo.OrderCode,
                Sign = null,
                Spbill_Create_Ip = _configuration["WechatPaied:Spbill_Create_Ip"],
                Total_Fee = 1,// Convert.ToInt32(orderinfo.TotalPrice * 100)
                Trade_Type = "JSAPI",
                OpenId = uinfo.OpenId
            };
            var type = wxUnifiedOrder.GetType();
            SortedDictionary<string, string> param = new SortedDictionary<string, string>();
            foreach (var item in type.GetProperties())
            {
                if (item.GetValue(wxUnifiedOrder) != null && item.Name != "Sign")
                {
                    param.Add(item.Name.ToLower(), item.GetValue(wxUnifiedOrder).ToString());
                }
            }
            List<string> lstparams = new List<string>();
            foreach (var item in param)
            {
                lstparams.Add(string.Concat(item.Key, "=", item.Value));
            }
            lstparams.Add(string.Concat("key", "=", _configuration["WechatPaied:Api_Key"]));
            string param_Sign = string.Join("&", lstparams);
            wxUnifiedOrder.Sign =param_Sign.MD5().ToUpper();//计算签名

这里的 SortedDictionary提供的就是一个排序后的参数列表，紧接着把他们按照排列好的顺序，拼起来，最后把key加上，调用.MD5这个扩展方法计算签名，把model填充起来

6.模拟请求一下微信提供的接口，执行统一下单，拿到返回值

string xmldoc = wxUnifiedOrder.ToXml(Encoding.UTF8);
var result = PostHttpResponse("https://api.mch.weixin.qq.com/pay/unifiedorder", xmldoc);
var resultData = result.ToXmlObject<WxUnifiedOrderResponse>(Encoding.UTF8);

PostHttpResponse 方法上文已提供 .ToXml .ToXmlObject上文也有提供,就是操作xml序列化的那两
6.1：WxUnifiedOrderResponse model内容：

 [System.SerializableAttribute()]
    [System.ComponentModel.DesignerCategoryAttribute("code")]
    [System.Xml.Serialization.XmlTypeAttribute(AnonymousType = true)]
    [System.Xml.Serialization.XmlRootAttribute(ElementName = "xml", Namespace = "", IsNullable = false)]
    public class WxUnifiedOrderResponse
    {
        /// <summary>
        /// 返回状态码
        /// </summary>
        [XmlElement(ElementName = "return_code")]
        public string Return_Code { get; set; }

        /// <summary>
        /// 返回信息
        /// </summary>
        [XmlElement(ElementName = "return_msg")]
        public string Return_Msg { get; set; }

        /// <summary>
        /// 小程序id
        /// </summary>
        [XmlElement(ElementName = "appid")]
        public string Appid { get; set; }

        /// <summary>
        /// 商户号
        /// </summary>
        [XmlElement(ElementName = "mch_id")]
        public string Mch_Id{get;set;}
        /// <summary>
        /// 随机字符串
        /// </summary>
        [XmlElement(ElementName = "nonce_str")]
        public string Nonce_Str { get; set; }
        /// <summary>
        /// 
        /// </summary>
        [XmlElement(ElementName = "openid")]
        public string Openid { get; set; }
        /// <summary>
        /// 微信返回的签名
        /// </summary>
        [XmlElement(ElementName = "sign")]
        public string Sign { get; set; }
        /// <summary>
        /// 业务结果
        /// </summary>
        [XmlElement(ElementName = "result_code")]
        public string Result_Code { get; set; }

        /// <summary>
        /// 预支付交易回话标识
        /// </summary>
        [XmlElement(ElementName = "prepay_id")]
        public string Prepay_Id { get; set; }
        /// <summary>
        /// 交易类型
        /// </summary>
        [XmlElement(ElementName = "trade_type")]
        public string Trade_Type { get; set; }
    }

7，再次签名

TimeSpan ts = DateTime.Now - new DateTime(1970, 1, 1, 0, 0, 0, 0);
            var wxPaidParams = new WxPaidParams()
            {
                appId = unifiedOrder.Data.Appid,
                nonceStr = unifiedOrder.Data.Nonce_Str,
                package = string.Concat("prepay_id=", unifiedOrder.Data.Prepay_Id),
                signType = "MD5",
                timeStamp = Convert.ToInt64(ts.TotalSeconds).ToString()
            };

            var type = wxPaidParams.GetType();
            SortedDictionary<string, string> param = new SortedDictionary<string, string>();
            foreach (var item in type.GetProperties())
            {
                if (item.GetValue(wxPaidParams) != null && item.Name != "paySign")
                {
                    param.Add(item.Name, item.GetValue(wxPaidParams).ToString());
                }
            }
            List<string> lstparams = new List<string>();
            foreach (var item in param)
            {
                lstparams.Add(string.Concat(item.Key, "=", item.Value));
            }
            lstparams.Add(string.Concat("key", "=", _configuration["WechatPaied:Api_Key"]));
            string param_paySign = string.Join("&", lstparams);
            wxPaidParams.paySign = param_paySign.MD5().ToUpper();

7.1  WxPaidParams

  public class WxPaidParams
    {
        /// <summary>
        /// appid
        /// </summary>
        public string appId { get; set; }
        /// <summary>
        /// 时间戳
        /// </summary>
        public string timeStamp { get; set; }
        /// <summary>
        /// 随机串
        /// </summary>
        public string nonceStr { get; set; }
        /// <summary>
        /// 数据包
        /// </summary>
        public string package { get; set; }
        /// <summary>
        /// 签名方式
        /// </summary>
        public string signType { get; set; }
        /// <summary>
        /// 签名
        /// </summary>
        public string paySign { get; set; }
    }

一毛一样，的道理，主逻辑写下来不到100行代码，将来统一下单地方的参数有变化，仅仅需要增加字段，赋值就可以，其他都不动，
再把下边那坨加密的东西再稍微封装一下，用到生产环境妥妥的。