wx.request({
        url: ‘https://api.weixin.qq.com/wxa/getwxacodeunlimit?access_token=‘ + token,
        method: "POST",
        responseType: ‘arraybuffer‘,
        data: {
          scene: 111, //这里填写url的参数，最大32个可见字符，只支持数字，大小写英文以及部分特殊字符：!#$&‘()*+,/:;=?@-._~
          page: ‘pages/index/index‘, //这里填写你要跳转的小程序页面，前面不能加/哦，必须为发布后的页面
          width: 1024 //小程序码的边长，单位px，范围[280,1280]
        },
        header: {
          ‘content-type‘: ‘application/json;charset=UTF-8‘
        },
        success(res) {
          var base64 = wx.arrayBufferToBase64(res.data);
          that.setData({
            qrCodeSrc: "data:image/png;base64," + base64
          });
        }
})

int scene = 0;
int.TryParse(context.Request.Params["scene"], out scene);

string access_token =...; //这里写你调用token的方法
if (access_token == "")
　　return "{\"errcode\":1,\"errmsg\":\"缺少access_token\"}";

            
string postUrl = "https://api.weixin.qq.com/wxa/getwxacodeunlimit?access_token=" + access_token;
HttpWebRequest request = WebRequest.Create(postUrl) as HttpWebRequest;
request.Method = "POST";
request.ContentType = "application/json;charset=UTF-8";

string options = "{\"scene\":\"" + scene + "\",\"page\":\"pages/index/index\",\"width\":\"1024\"}";
byte[] payload = Encoding.UTF8.GetBytes(options);
request.ContentLength = payload.Length;

Stream writer = request.GetRequestStream();
writer.Write(payload, 0, payload.Length);
writer.Close();

System.Net.HttpWebResponse response = (System.Net.HttpWebResponse)request.GetResponse();
System.IO.Stream stream = response.GetResponseStream();
List<byte> bytes = new List<byte>();
int temp = stream.ReadByte();
while (temp != -1)
{
　　bytes.Add((byte)temp);
　　temp = stream.ReadByte();
}
byte[] result = bytes.ToArray();
string base64 = Convert.ToBase64String(result);//将byte[]转为base64
return "{\"errcode\":0,\"errmsg\":\"获取成功\",\"buffer\":\"" + base64 + "\"}";

onLoad: function (options) {
    var id = options.id || decodeURIComponent(options.scene);
　　//options.id是页面url参数，options.scene是扫码带入的参数
}