sending attachment file to email using c#

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C#

My code as follows

private void btn_Sendmail_Click(object sender, EventArgs e)
        {
            try
            {
                MailMessage mail = new MailMessage();
                SmtpClient smtpserver = new SmtpClient("smtp.gmail.com");
                mail.From = new MailAddress("noreply@himtmarine.com", "reminder mail");
                mail.To.Add("ns@himtmarine.com");
                mail.Subject = "Reminder";
                mail.Body = "mail with attachment";

                System.Net.Mail.Attachment attachment;
                attachment = new System.Net.Mail.Attachment("E:/Projects/Book1.xls");
                mail.Attachments.Add(Attachment);

                smtpserver.Credentials = new NetworkCredential("ns@himtmarine.com", "himt1234");
                smtpserver.Port = 587;
                smtpserver.EnableSsl = true;

                smtpserver.Send(mail);
                MessageBox.Show("mail send");
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }


        }

when i run this code says error as follows
System.Net.Mail.Attachment' is a 'type' but is used like a 'variable'

error shows in below line as follows
mail.Attachments.Add(Attachment);

please help me.

what is the problem. in my code.

Rgds,
Narasiman P