How to add inline image in Outlook appointment in code behind C#?

LinkedResource inline = new LinkedResource(filePath);
            inline.ContentId = Guid.NewGuid().ToString();
            MailMessage mail = new MailMessage();
            Attachment att = new Attachment(filePath);
            att.ContentDisposition.Inline = true;
            mail.From = from_email;
            mail.To.Add(data.email);
            mail.Subject = "Client: " + data.client_id + " Has Sent You A Screenshot";
            mail.Body = String.Format(
                "<h3>Client: " + data.client_id + " Has Sent You A Screenshot</h3>" +
                @"<img src=""cid:{0}"" />", inline.ContentId);

            mail.IsBodyHtml = true;
            mail.Attachments.Add(att);