I want to send email id from my mail to the email entered in textbox

public  void sendmail(string toAddr)
{
    string to = toAddr;
    string from = "xyz@gmail.com";
    MailMessage message = new MailMessage(from,to);
    
    message.Subject = "This is my subject";

    message.Body = "This is the content";

    SmtpClient client = new SmtpClient();
           
    client.Send(message);
}

protected void sendBtn_Click(object sender, EventArgs e)
{
    sendMail(TextBox2.Text);
}

try
            {
                string to = TextBox2.Text;
                string from = "xyz@gmail.com";


                MailMessage mail = new MailMessage();
                SmtpClient SmtpServer = new SmtpClient("smtp.gmail.com");
 
                mail.From = new MailAddress("me@mydomain.com");
                mail.To.Add(to);
                mail.Subject = "This is my subject";
                mail.Body = "This is the content";
                Attachment attachment = new Attachment(filename);
                mail.Attachments.Add(attachment);
 
                SmtpServer.Port = 25;
                SmtpServer.Credentials = new System.Net.NetworkCredential("Username", "password");
                SmtpServer.EnableSsl = true;
 
                SmtpServer.Send(mail);
            }