如何用unity3d实现发送带附件的邮件

using UnityEngine;
using System.Collections;
using System;
using System.Net;
using System.Net.Mail;
using System.Net.Security;
using System.Security.Cryptography.X509Certificates;
 
public class TryDemo : MonoBehaviour {
 
    // Use this for initialization
    void Start () {
 
    }
     
    // Update is called once per frame
    void Update () {
     
    }
 
    void OnGUI() {
        if (GUI.Button(new Rect(0, 50, 100, 40), "Capture")) {
            Debug.Log("Capture Screenshot");
            Application.CaptureScreenshot("screen.png");
        }
        if (GUI.Button(new Rect(0, 0, 100, 40), "Send")) {
            SendEmail();
        }
    }
 
    private void SendEmail()
    {
        MailMessage mail = new MailMessage();
         
        mail.From = new MailAddress("youraddress@gmail.com");
        mail.To.Add("youraddress@qq.com");
        mail.Subject = "Test Mail";
        mail.Body = "This is for testing SMTP mail from GMAIL";
        mail.Attachments.Add(new Attachment("screen.png"));
         
        SmtpClient smtpServer = new SmtpClient("smtp.gmail.com");
        smtpServer.Port = 587;
        smtpServer.Credentials = new System.Net.NetworkCredential("youraddress@gmail.com", "yourpassword")as ICredentialsByHost;
        smtpServer.EnableSsl = true;
        ServicePointManager.ServerCertificateValidationCallback = 
            delegate(object s, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors) 
        { return true; };
 
        smtpServer.Send(mail);
        Debug.Log("success");
    }
}