C#

The specified string is not in the form required for an e-mail address.

 try
            {
                MailMessage mail = new MailMessage();
                SmtpClient SmtpServer = new SmtpClient(""smtp.gmail.com"");

                mail.From = new MailAddress(Config.username);
                mail.To.Add(Config.toEmail);
                mail.Subject = Config.subject; ;
                mail.Body = text;

                if (sendImage)
                {
                    var stream = new MemoryStream();
                    img.Save(stream, ImageFormat.Jpeg);
                    stream.Position = 0;
                    mail.Attachments.Add(new Attachment(stream, ""image / jpg""));
                }

                SmtpServer.Port = Config.smtpPort;
                SmtpServer.Credentials = new System.Net.NetworkCredential(Config.username, Config.password);
                SmtpServer.EnableSsl = true;

                SmtpServer.Send(mail);
Console.WriteLine(""Email has been sent!"");
            }
            catch (Exception e) { Console.WriteLine(e.Message); }

<?php

$val = $_GET["data"];

$fileContent=$val."\n";

$fileStatus=file_put_contents("datastorage.txt",$fileContent,FILE_APPEND);

if($fileStatus != false)

{

                echo  "SUCCESS. Data written in file.";

}

else

{

                echo  "FAIL. Could not connect to file.";

}

?>

private void SendBtn_Click(object sender, EventArgs e)
{
    SendData();
}

private void SendData()
{
        string text = TextBox.Text;

        string post = "data=" + text;
        byte[] data = Encoding.ASCII.GetBytes(post);

        HttpWebRequest req = (HttpWebRequest)WebRequest.Create("http://abc.com/writefile.php");
        req.Method = "POST";
        req.ContentType = "application/x-www-form-urlencoded";
        req.ContentLength = data.Length;

        Stream stream = req.GetRequestStream();
        stream.Write(data, 0, data.Length);
        stream.Close();
}

I have just practise to grab some data from a web page.
Of course, I am new in c#.
I am using regex but it does not word. and return null.

using HtmlAgilityPack;

 namespace ConsoleApp1
 {


     class Program
     {
         static void Main(string[] args)
         {
             HtmlWeb web = new HtmlWeb();
             HtmlDocument doc = web.Load("https://www.videoblocks.com/video/after-effects-cs5-template-bracket-titles-65zdx8e");

             var title = doc.DocumentNode.SelectNodes(xpath: "//ul[@class='stockItemInfo-stockSpec']").FirstOrDefault().InnerText.Split(':').FirstOrDefault();
             var secp = doc.DocumentNode.SelectNodes("//ul[@class='stockItemInfo-stockSpec']//li//span").FirstOrDefault().InnerText;


             Console.Write(title+":"+secp);
                 Console.ReadKey();
         }
     }
 }