How to submit http form using C

Question

I have a simple html file such as   lt form action  http   www someurl com page php  method  POST  gt      lt input type  text  name  test  gt  lt br  gt      lt input type  submit  name  submit  gt   lt  form gt    Edit  I may not have been clear enough with the question  I want to write C  code which submits this form in the exact same manner that would occur had I pasted the above html into a file  opened it with IE and submitted it with the browser

User · Answer

Your HTML file is not going to interact with C# directly, but you can write some C# to behave as if it were the HTML file.

For example: there is a class called System.Net.WebClient with simple methods:

using System.Net;
using System.Collections.Specialized;

...
using(WebClient client = new WebClient()) {

    NameValueCollection vals = new NameValueCollection();
    vals.Add("test", "test string");
    client.UploadValues("http://www.someurl.com/page.php", vals);
}

For more documentation and features, refer to the MSDN page.

User · Answer

Here is a sample script that I recently used in a Gateway POST transaction that receives a GET response   Are you using this in a custom C  form   Whatever your purpose  just replace the String fields  username  password  etc   with the parameters from your form   private String readHtmlPage string url              setup some variables      String username     demo       String password     password       String firstname    John       String lastname     Smith          setup some variables end        String result             String strPost    username   username   amp password   password   amp firstname   firstname   amp lastname   lastname        StreamWriter myWriter   null         HttpWebRequest objRequest    HttpWebRequest WebRequest Create url         objRequest Method    POST         objRequest ContentLength   strPost Length        objRequest ContentType    application x-www-form-urlencoded          try                  myWriter   new StreamWriter objRequest GetRequestStream              myWriter Write strPost                 catch  Exception e                    return e Message                finally            myWriter Close                   HttpWebResponse objResponse    HttpWebResponse objRequest GetResponse          using  StreamReader sr             new StreamReader objResponse GetResponseStream                       result   sr ReadToEnd                 Close and clean up the StreamReader          sr Close                  return result

User · Answer

I needed to have a button handler that created a form post to another application within the client s browser  I landed on this question but didn t see an answer that suited my scenario  This is what I came up with         protected void Button1 Click object sender  EventArgs e                         var formPostText      lt html gt  lt body gt  lt div gt   lt form method   POST   action   OtherLogin aspx   name   frm2Post   gt     lt input type   hidden   name   field1   value       TextBox1 Text          gt      lt input type   hidden   name   field2   value       TextBox2 Text          gt    lt  form gt  lt  div gt  lt script type   text javascript   gt document frm2Post submit    lt  script gt  lt  body gt  lt  html gt                 Response Write formPostText

User · Answer

You can use the HttpWebRequest class to do so   Example here   using System  using System Net  using System Text  using System IO        public class Test                  Specify the URL to receive the request          public static void Main  string   args                        HttpWebRequest request    HttpWebRequest WebRequest Create  args 0                    Set some reasonable limits on resources used by this request             request MaximumAutomaticRedirections   4              request MaximumResponseHeadersLength   4                 Set credentials to use for this request              request Credentials   CredentialCache DefaultCredentials              HttpWebResponse response    HttpWebResponse request GetResponse                  Console WriteLine   Content length is  0    response ContentLength               Console WriteLine   Content type is  0    response ContentType                   Get the stream associated with the response              Stream receiveStream   response GetResponseStream                     Pipes the stream to a higher level stream reader with the required encoding format               StreamReader readStream   new StreamReader  receiveStream  Encoding UTF8                Console WriteLine   Response stream received                 Console WriteLine  readStream ReadToEnd                  response Close                 readStream Close                         The output from this example will vary depending on the value passed into Main  but will be similar to the following   Content length is 1542 Content type is text html  charset utf-8 Response stream received   lt html gt       lt  html gt

User · Answer

Response Write   lt script gt  try  this submit     catch e     lt  script gt

User · Answer

I had a similar issue in MVC  which lead me to this problem    I am receiving a FORM as a string response from a WebClient UploadValues   request  which I then have to submit - so I can t use a second WebClient or HttpWebRequest  This request returned the string   using  WebClient client   new WebClient            byte   response   client UploadValues urlToCall   POST   new NameValueCollection                    test    value123                 result   System Text Encoding UTF8 GetString response         My solution  which could be used to solve the OP  is to append a Javascript auto submit to the end of the code  and then using  Html Raw   to render it on a Razor page   result      lt script gt self document forms 0  submit   lt  script gt    someModel rawHTML   result  return View someModel     Razor Code    model SomeModel         Layout   null      Html Raw  Model rawHTML    I hope this can help anyone who finds themselves in the same situation

[c#] How to submit http form using C#

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