Question

So got an small problem. Im creating an small application to automate an form submission on one website. But the bad thing is that they are using multipart/form-data for that. There is no file uploading just some text fields for submission.

Of course doing it like this it fails.

string postData1 = "firstfield="+firststring+"secondfield="+secondstring;

So my question is how the hell post those form fields with multipart form?

Posting like arrays in php like this:

$postdata = array( firstfield => $firststring, secondfield => $secondstring);

works and passes the form but seems not working with c#

Any suggestions?

Data submission goes through 3 page ( basic screenscrape ) login/part1/part2

So far i can log in successfully and post part1 (uses normal application/x-www-form-urlencoded form )

But when ill try to post multipart form it fails and sends me back to part1. So maybe is my code wrong but here it is:

string password = "password";
string username = "username";
string link = "http://somelink.com/";
string text = "Blah Blah some text here";
string title = "Blah Blah";
string tags1 = title;
string summary = "Blah Blah summary";
string tags = tags1.Replace(" ", ",");

// Set cookie container
CookieContainer cookieJar = new CookieContainer();

string loginData = "username=" + username + "&password=" + password + "&processlogin=1&return=%2Fsubmit.php";

HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create("http://loginlink.com/login.php");
myRequest.Method = "POST";
        myRequest.ServicePoint.Expect100Continue = false;
myRequest.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.4) Gecko/20091016 Firefox/3.5.4 GTB6 (.NET CLR 3.5.30729)";
myRequest.Timeout = 10000;
myRequest.ContentType = "application/x-www-form-urlencoded";
myRequest.ContentLength = loginData.Length;
myRequest.CookieContainer = cookieJar;
myRequest.KeepAlive = true;
myRequest.AllowAutoRedirect = true;

//Write post data to stream
StreamWriter myWriter = new StreamWriter(myRequest.GetRequestStream());
myWriter.Write(loginData);
myWriter.Close();

// Get the response.
HttpWebResponse myResponse = (HttpWebResponse)myRequest.GetResponse();

// Open the stream using a StreamReader for easy access.
StreamReader myReader = new StreamReader(myResponse.GetResponseStream());
// Read the content.
string output = myReader.ReadToEnd();

// Clean up the streams and the response.
myReader.Close();
myResponse.Close();


Match matchkey = Regex.Match(output, "type="hidden" name="randkey" value="([^"]+)"", RegexOptions.IgnoreCase);
string key1 = matchkey.Groups[1].Value;
Match matchid = Regex.Match(output, "type="hidden" name="id" value="([^"]+)"", RegexOptions.IgnoreCase);
string id1 = matchid.Groups[1].Value;


string postData = "url=" + link + "&phase=1&randkey=" + key1 + "&id=" + id1;

HttpWebRequest myRequest2 = (HttpWebRequest)WebRequest.Create("http://submitpage1.com/submit.php");
myRequest2.Method = "POST";
myRequest2.ServicePoint.Expect100Continue = false;
myRequest2.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.4) Gecko/20091016 Firefox/3.5.4 GTB6 (.NET CLR 3.5.30729)";
myRequest2.Timeout = 10000;
myRequest2.ContentType = "application/x-www-form-urlencoded";
myRequest2.ContentLength = postData.Length;
myRequest2.CookieContainer = cookieJar;
myRequest2.KeepAlive = true;
myRequest2.AllowAutoRedirect = true;


//Write post data to stream
StreamWriter myWriter2 = new StreamWriter(myRequest2.GetRequestStream());
myWriter2.Write(postData);
myWriter2.Close();

// Get the response.
HttpWebResponse myResponse2 = (HttpWebResponse)myRequest2.GetResponse();

// Open the stream using a StreamReader for easy access.
StreamReader myReader2 = new StreamReader(myResponse2.GetResponseStream());
// Read the content.
string output1 = myReader2.ReadToEnd();

// Clean up the streams and the response.
myReader2.Close();
myResponse2.Close();

Match matchkey1 = Regex.Match(output1, "type="hidden" name="randkey" value="([^"]+)"", RegexOptions.IgnoreCase);
string key2 = matchkey1.Groups[1].Value;
Match matchid1 = Regex.Match(output1, "type="hidden" name="randkey" value="([^"]+)"", RegexOptions.IgnoreCase);
string id2 = matchid1.Groups[1].Value;

string boundary = "-----------------------------1721856231228";

// Build up the post
StringBuilder sb = new StringBuilder();
sb.Append("
" + boundary + "
");
sb.Append("Content-Disposition: form-data; name="title"" + "
");
sb.Append("
");
sb.Append(title);
sb.Append("
--" + boundary + "
");
sb.Append("Content-Disposition: form-data; name="tags"" + "
");
sb.Append("
");
sb.Append(tags);
sb.Append("
--" + boundary + "
");
sb.Append("Content-Disposition: form-data; name="bodytext"" + "
");
sb.Append("
");
sb.Append(text);
sb.Append("
--" + boundary + "
");
sb.Append("Content-Disposition: form-data; name="summarycheckbox"" + "
");
sb.Append("
");
sb.Append("on");
sb.Append("
--" + boundary + "
");
sb.Append("Content-Disposition: form-data; name="summarytext"" + "
");
sb.Append("
");
sb.Append(summary);
sb.Append("
--" + boundary + "
");
sb.Append("Content-Disposition: form-data; name="remLen"" + "
");
sb.Append("
");
sb.Append("125");
sb.Append("
--" + boundary + "
");
sb.Append("Content-Disposition: form-data; name="category"" + "
");
sb.Append("
");
sb.Append("1");
sb.Append("
--" + boundary + "
");
sb.Append("Content-Disposition: form-data; name="trackback"" + "
");
sb.Append("
");
sb.Append("");
sb.Append("
--" + boundary + "
");
sb.Append("Content-Disposition: form-data; name="url"" + "
");
sb.Append("
");
sb.Append(link);
sb.Append("
--" + boundary + "
");
sb.Append("Content-Disposition: form-data; name="phase"" + "
");
sb.Append("
");
sb.Append("2");
sb.Append("
--" + boundary + "
");
sb.Append("Content-Disposition: form-data; name="randkey"" + "
");
sb.Append("
");
sb.Append(key2);
sb.Append("
--" + boundary + "
");
sb.Append("Content-Disposition: form-data; name="id"" + "
");
sb.Append("
");
sb.Append(id2);
sb.Append("
--" + boundary + "--" + "
");

string postData1 = sb.ToString();

HttpWebRequest myRequest3 = (HttpWebRequest)WebRequest.Create("http://submitpage2.com/submit.php");
myRequest3.Method = "POST";
myRequest3.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.4) Gecko/20091016 Firefox/3.5.4 GTB6 (.NET CLR 3.5.30729)";
myRequest3.Timeout = 10000;
myRequest3.ServicePoint.Expect100Continue = false;
myRequest3.Referer = "http://bookmarkindo.com/submit.php";
myRequest3.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";
myRequest3.ContentType = "multipart/form-data; boundary=" + boundary;
myRequest3.ContentLength = postData1.Length;
myRequest3.CookieContainer = cookieJar;
myRequest3.KeepAlive = true;
myRequest3.AllowAutoRedirect = true;

//Write out postdata
StreamWriter myWriter3 = new StreamWriter(myRequest3.GetRequestStream());
myWriter3.Write(postData1);
myWriter3.Close();

// Get the response.
HttpWebResponse myResponse3 = (HttpWebResponse)myRequest3.GetResponse();

// Open the stream using a StreamReader for easy access.
StreamReader myReader3 = new StreamReader(myResponse3.GetResponseStream());
// Read the content.
string output2 = myReader3.ReadToEnd();

// Clean up the streams and the response.
myReader3.Close();
myResponse3.Close();

All suggestions are welcome

Answer 1

posts os multipart/form-data type have a different structure because they are meant to transfer data and not just plain text.

Here s the format:

--[random number, a GUID is good here]
Content-Disposition: form-data; name="[name of variable]"

[actual value]
--[random number, a GUID is good here]--

Using HTTPWebRequest you can create a request that has that format. Here s a sample:

string boundary = Guid.NewGuid().ToString();
string header = string.Format("--{0}", boundary);
string footer = string.Format("--{0}--", boundary);

StringBuilder contents = new StringBuilder();
contents.AppendLine(header);

contents.AppendLine(header);
contents.AppendLine(String.Format("Content-Disposition: form-data; name="{0}"", "username"));
contents.AppendLine();
contents.AppendLine("your_username");

contents.AppendLine(header);
contents.AppendLine(String.Format("Content-Disposition: form-data; name="{0}"", "password"));
contents.AppendLine();
contents.AppendLine("your_password");

contents.AppendLine(footer);

Answer 2

The best way to send multipart form data in C# is shown in the snippet, here you see that adding different type of content is as easy as adding it to the wrapper multipart content type:

var documentContent = new MultipartFormDataContent();
documentContent.Add(new StringContent("AnalyticsPage.xlsx"), "title");
documentContent.Add(new ByteArrayContent(File.ReadAllBytes("C:\Users\awasthi\Downloads\AnalyticsPage.xlsx")), "file", "AnalyticsPage.xlsx");

Then just make an api call:

using (var client = new HttpClient(new HttpClientHandler() { UseDefaultCredentials = true, CookieContainer = new CookieContainer() }))
{
  response = client.PostAsync(documentAddApi, documentContent).Result;
  var responseContent = response.Content.ReadAsStringAsync().Result;
 }

Here the expectation is that the rest endpoint you are making a call to is accepting a title field for the file and the byte array of the file named file .

Answer 3

Here is an article on multipart form posts in C# with more detail. This code was eventually merged into RestSharp, which is an excellent library you could use to generate the request.

Answer 4

The format of multipart/form-data requests is outlined here: http://www.w3.org/TR/html401/interact/forms.html#h-17.13.4.2.

友情链接