我如何从 aspx 网站 __doPostBack 表单中抓取数据？

Question

I'm trying to crawl/scrape a website using c# console app, getting the initial page is not a problem, but I need to get pages when I click on the button who has the __doPostBack action.

I try with these settings but this already back results from the initial page:

I Update my code

            var client1 = new RestClient("https://example.com");
            var request1 = new RestRequest(Method.POST);
            IRestResponse initialResponse = client1.Execute(request1);


            HtmlDocument doc = new HtmlDocument();
            doc.LoadHtml(initialResponse.Content);

            var formData = new Dictionary<string, string>();
            formData.Add("__EVENTTARGET", "ctl00$MainContentExample");
            formData.Add("__EVENTARGUMENT", "");
            formData.Add("ctl00$MainContent$CustomHiddenField", "");
            formData.Add("__VIEWSTATEGENERATOR", "B5682C7D");
            var divViewState = doc.DocumentNode
                .SelectSingleNode("//input[@name='__VIEWSTATE']").Attributes[3].Value;
            formData.Add("__VIEWSTATE", divViewState);
            var divEventValidation = doc.DocumentNode
                .SelectSingleNode("//input[@name='__EVENTVALIDATION']").Attributes[3].Value;
            formData.Add("__EVENTVALIDATION", divEventValidation);


            var client = new RestClient("https://example.com");
            var request = new RestRequest("/methodName",Method.POST);
            request.AddHeader("cache-control", "no-cache");
            request.AddHeader("Connection", "keep-alive");

            var c = "";
            var i = 0;
            foreach (var cookie in initialResponse.Cookies)
            {
                if(i==0)
                 c += cookie.Name + "=" + cookie.Value + "; ";
                else
                    c += cookie.Name + "=" + cookie.Value;

                i++;
            }
            request.AddHeader("Cookie", c);
           request.AddHeader("Accept-Encoding", "gzip, deflate, br");
            request.AddHeader("Host", "example.com");
            request.AddHeader("Cache-Control", "max-age=0");
            request.AddHeader("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3");
            request.AddHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36");
            request.AddHeader("Content-Type", "application/x-www-form-urlencoded");
            request.AddHeader("Accept-Language", "en-US,en;q=0.9");
            request.AddHeader("Content-Encoding", "utf-8");

            var json = JsonConvert.SerializeObject(formData);
            byte[] byteData = Encoding.UTF8.GetBytes(json);

            request.AddHeader("Content-Length", byteData.Length.ToString())


            request.AddParameter("undefined", byteData, ParameterType.RequestBody);

            IRestResponse response2 = client.Execute(request);

Answer 1

Use RestRequest.AddParameter instead of RestRequest.AddHeader

https://csharp.hotexamples.com/examples/RestSharp/RestRequest/AddHeader/php-restrequest-addheader-method-examples.html

https://csharp.hotexamples.com/examples/RestSharp/RestRequest/AddParameter/php-restrequest-addparameter-method-examples.html