Send Uploaded File as attachment

I am trying to get an uploaded file to be sent as an attachment in my ashx file. Here is the code I am using:

HttpPostedFile fileupload = context.Request.Files[0];

//filename w/o the path
string file = Path.GetFileName(fileupload.FileName);

MailMessage message = new MailMessage();

//*****useless stuff********
message.To.Add("abc@xxx.com");
message.Subject = "test";
message.From = new MailAddress("test@aaa.com");
message.IsBodyHtml = true;
message.Body = "testing";
 //*****useless stuff********

//Fault line
message.Attachments.Add(new Attachment(file, MediaTypeNames.Application.Octet))

//Send mail 
SmtpClient smtp = new System.Net.Mail.SmtpClient("xxxx", 25);
smtp.UseDefaultCredentials = false;
smtp.Credentials = new NetworkCredential("xxx", "xxxx");
smtp.Send(message);

I am able to send the email without the attachment. Do I need to save the file first and then add to attachment?