Well, if you can crack the captcha (never tried to do it) sending the parameters to a web form from c# it's pretty easy, doable in like 20 lines max.
A simple search on Google returned that :
Code:
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+"&password="+password+"&firstname="+firstname+"&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;
}
And with a few tweaks it works (I know it does, I used it before TQ added CAPTCHA).
Now all you need more is adding the CAPTCHA response. If you can't crack it, there are some paid services available, one of them being

, offering an easy C# API for that.