How to write a HTTP Request

Question

Hello I try to write a HTTP Request in C# (Post), but I need help with an error

Expl: I want to send the Content of a DLC File to the Server and recive the decrypted content.

C# Code

public static void decryptContainer(string dlc_content) 
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://dcrypt.it/decrypt/paste");
    request.Method = "POST";
    request.ContentType = "application/x-www-form-urlencoded";
    request.Accept = "Accept=text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";

    using (StreamWriter writer = new StreamWriter(request.GetRequestStream(), Encoding.ASCII))
    {
        writer.Write("content=" + dlc_content);
    }

    HttpWebResponse response = (HttpWebResponse)request.GetResponse();

    using (StreamReader reader = new StreamReader(response.GetResponseStream()))
    {
        Console.WriteLine(reader.ReadToEnd());
    }
}

and here I got the html request

<form action="/decrypt/paste" method="post">
    <fieldset>
        <p class="formrow">
          <label for="content">DLC content</label>
          <input id="content" name="content" type="text" value="" />
         </p>
        <p class="buttonrow"><button type="submit">Submit »</button></p>
    </fieldset>
</form>

Error Message:

{
    "form_errors": {
      "__all__": [
        "Sorry, an error occurred while processing the container."
       ]
    }
}

Would be very helpfull if someone could help me solving the problem!

Answer 1

You haven't set a content-length, which might cause issues. You could also try writing bytes directly to the stream instead of converting it to ASCII first.. (do it the opposite way to how you're doing it at the moment), eg:

public static void decryptContainer(string dlc_content) 
   {
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://dcrypt.it/decrypt/paste");
        request.Method = "POST";
        request.ContentType = "application/x-www-form-urlencoded";
        request.Accept = "Accept=text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";

        byte[] _byteVersion = Encoding.ASCII.GetBytes(string.Concat("content=", dlc_content));

        request.ContentLength = _byteVersion.Length

        Stream stream = request.GetRequestStream();
        stream.Write(_byteVersion, 0, _byteVersion.Length);
        stream.Close();

        HttpWebResponse response = (HttpWebResponse)request.GetResponse();

        using (StreamReader reader = new StreamReader(response.GetResponseStream()))
        {
            Console.WriteLine(reader.ReadToEnd());
        }
    }

I've personally found posting like this to be a bit "fidgity" in the past. You could also try setting the ProtocolVersion on the request.

Answer 2

I would simplify your code, like this:

public static void decryptContainer(string dlc_content) 
{
    using (var client = new WebClient())
    {
        var values = new NameValueCollection
        {
            { "content", dlc_content }
        };
        client.Headers[HttpRequestHeader.Accept] = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";
        string url = "http://dcrypt.it/decrypt/paste";
        byte[] result = client.UploadValues(url, values);
        Console.WriteLine(Encoding.UTF8.GetString(result));
    }
}

It also ensures that the request parameters are properly encoded.