sending an email with attachment in .net core console application

I need to send an email with attachment in .net core console application. The part of sending an email is working. The attachment part is not working. I have this code:

public void sendEmail(List<string> toList)

    {

        string from = "******@test.com";

        string UserName = ConfigurationManager.AppSettings["UserName"].ToString();

        string password = ConfigurationManager.AppSettings["password"].ToString();

        string PathToAttachment = ConfigurationManager.AppSettings["AttachPath"].ToString();

       

        foreach (var item in toList)

        {

            using (MailMessage mm = new MailMessage())

            {

                mm.From = new MailAddress(from);

                mm.To.Add(new MailAddress("******@test.com"));

                Attachment attachment = new Attachment(PathToAttachment);

                mm.Attachments.Add(attachment);

                mm.Subject = "this is test";

                mm.Body = GetEmailBody();

                mm.IsBodyHtml = true;

                SmtpClient client = new SmtpClient();

                client.Credentials = new NetworkCredential(UserName, password);

                client.Port = 200;

                client.EnableSsl = true;

                client.Host = "smtp.office365.com";

                client.DeliveryMethod = SmtpDeliveryMethod.Network;

                client.Send(mm);

            }

        }

    }

pathToAttachment is: C:\NotificationService\Attachments

The file that needs to be attached is stored inside the application in a folder called attachment. below is the structure:

NotificationService is the project name and I need to attach test.pdf file in an email attachment. I am getting an error saying:

Please let me know how can I send an attachment in .net core console application.