string UserName = "the_crazed";
            string Password = "password";
            string LoginUrl = "http://localhost:3871/FormsAuth/Login.aspx";
            string RequiredUrl = "/FormsAuth/Default.aspx?arg1=arg";
            
	        ASCIIEncoding encoding=new ASCIIEncoding();
            string postData = "__EVENTTARGET=&__EVENTARGUMENT=";
            postData += ("&__VIEWSTATE=" + HttpUtility.UrlEncode("/wEPDwUJMzE3NDg1ODg2ZBgBBR5fX0NvbnRyb2xzUmVxdWlyZVBvc3RCYWNrS2V5X18WAQUHUGVyc2lzdGK4YPE96Ga3K7tCkMvgfg0xROmy"));
            postData += ("&UserEmail=" + UserName);
            postData += ("&UserPass=" + Password);
            postData += ("&Submit1=Log On");
            postData += ("&__EVENTVALIDATION=" + HttpUtility.UrlEncode("/wEWBgLnqtcEAqDzmJ4CAtSlzfsMAs/KzOANAt+L2uIOAtWjxq8OWVnf5o/N3BipezywbAuTJebjbRc="));
	        byte[]  data = encoding.GetBytes(postData);
 
            System.Net.Cookie c = new Cookie("DUMMY", "");
            Uri u = new Uri(LoginUrl + "?ReturnUrl=" + HttpUtility.UrlEncode(RequiredUrl));
            MessageBox.Show(u.AbsoluteUri);
            System.Net.HttpWebRequest w = (HttpWebRequest)System.Net.WebRequest.Create(u);
 
            w.Referer = "http://localhost:3871/FormsAuth/Login.aspx";
            w.CookieContainer = new CookieContainer();
            w.CookieContainer.Add(u, c);
 
            w.Method = "POST";
	        w.ContentType="application/x-www-form-urlencoded";
	        w.ContentLength = data.Length;
	        Stream newStream=w.GetRequestStream();
	        // Send the data.
	        newStream.Write(data,0,data.Length);
	        newStream.Close();
            w.Credentials = System.Net.CredentialCache.DefaultCredentials;
            string str = "";
            try
            {
                WebResponse r = w.GetResponse();
                Stream s = r.GetResponseStream();
                StreamReader reader = new StreamReader(s);
                str = reader.ReadToEnd();
            }
            catch (Exception ex)
            {
                str=ex.Message;
 
            }
 
            MessageBox.Show(str);