private void button1_Click(object sender, EventArgs e)//sender { string appSign = "UrfaDiyarbakir"; if (listBox1.SelectedIndex >= 0) { char[] charsToTrim = { ' ', '"' }; int index = listBox1.SelectedIndex; var dateTime = DateTime.Now; string mailfrom = logformobj.getUsrName(); string mailpass = logformobj.getUsrPass(); try { string encryptedAESkey = friends[index, 0].Trim(charsToTrim); string decryptedAESkey = RSAobj.Decrypt(encryptedAESkey); string mailTo = friends[index, 2].Trim(charsToTrim); var post = new MailMessage(mailfrom, mailTo); string MailSign = textBox1.Text + "\n" + dateTime; string cryptedMailSign = RSAobj.SignData(MailSign); post.Subject = AesCrypt.EncryptParam(textBox2.Text, decryptedAESkey); post.Body = AesCrypt.Encrypt(appSign) + "---AppSign---" + AesCrypt.Encrypt(EncryptedMailApp.LoginForm.user) + "---Username---" + AesCrypt.EncryptParam(textBox1.Text + "\n" + dateTime, decryptedAESkey) + "---Body---" + cryptedMailSign + "---Sign---"; ; using (SmtpClient smtp = new SmtpClient("smtp.gmail.com", 587)) { smtp.Credentials = new NetworkCredential(mailfrom, mailpass); smtp.EnableSsl = true; if (!string.IsNullOrEmpty(textBox3.Text)) { EncryptedMailApp.CryptoStuff.EncryptFile(password, textBox3.Text, textBox3.Text + "crp"); Attachment data = new Attachment(textBox3.Text + "crp"); post.Attachments.Add(data); smtp.Send(post); MessageBox.Show("Email Sent With Attachment"); } else { smtp.Send(post); MessageBox.Show("Email Sent"); } } } catch { MessageBox.Show("ERROR"); } } else { MessageBox.Show("There is no selected friend!"); } }