webapi通过微信api获取二维码buffer流转换成图片保存到本地

前言：微信小程序需要生成二维码，后台通过微信api获取buffer流转换成图片保存到本地。以下代码直接返回图片地址

  public static string Api_Post(string postUrl, string postData, WebHeaderCollection header = null, bool isPic = false)
        {
            Stream outstream = null;
            Stream instream = null;
            StreamReader sr = null;
            HttpWebResponse response = null;
            HttpWebRequest request = null;
            Encoding encoding = Encoding.UTF8;
            byte[] data = encoding.GetBytes(postData);
            // 准备请求...
            try
            {
                // 设置参数
                request = WebRequest.Create(postUrl) as HttpWebRequest;
                CookieContainer cookieContainer = new CookieContainer();
                request.CookieContainer = cookieContainer;
                request.AllowAutoRedirect = true;
                request.Method = "POST";
                request.ContentType = "application/json";
                if (header != null) request.Headers = header;
                request.ContentLength = data.Length;
                outstream = request.GetRequestStream();
                outstream.Write(data, 0, data.Length);
                outstream.Close();
                //发送请求并获取相应回应数据
                response = request.GetResponse() as HttpWebResponse;
                //直到request.GetResponse()程序才开始向目标网页发送Post请求
                instream = response.GetResponseStream();

                if (isPic)
                {
                    byte[] tt = StreamToBytes(instream);//将数据流转为byte[]
                    string guid = Guid.NewGuid().ToString();
                    System.IO.File.WriteAllBytes(HttpContext.Current.Server.MapPath("~/Content/img/"+ guid + ".jpg"), tt);
                   
                    return "https://*********/Content/img/" + guid + ".jpg";
                }
                else
                {
                    sr = new StreamReader(instream, encoding);
                    //返回结果网页（html）代码
                    string content = sr.ReadToEnd();
                    string err = string.Empty;
                    return content;
                }

            }
            catch (Exception ex)
            {
                if (isPic)
                {
                    sr = new StreamReader(instream, encoding);
                    //返回结果网页（html）代码
                    string content = sr.ReadToEnd();
                    string err = string.Empty;
                    return content;
                }
                else
                {
                    string err = ex.Message;
                    return string.Empty;
                }
            }
        }

  ///将数据流转为byte[]
        public static byte[] StreamToBytes(Stream stream)
        {
            List<byte> bytes = new List<byte>();
            int temp = stream.ReadByte();
            while (temp != -1)
            {
                bytes.Add((byte)temp);
                temp = stream.ReadByte();
            }
            return bytes.ToArray();
        }

 

调用上面Api_Post方法

 string strUrlPara = "{\"page\":\"" + page + "\",\"scene\":" + scene + "}";
 string url= "https://api.weixin.qq.com/wxa/getwxacodeunlimit?access_token=**************";
 string resu = Api_Post(url, strUrlPara, null, true);