关于C＃using语句，我做对了吗？

Question

both SmtpClient and MailMessage implements IDisposable so i thought of making my code like this

using (SmtpClient smtpClient = new SmtpClient("xxx", 587))
{
    smtpClient.Credentials = new System.Net.NetworkCredential("email", "pass");
    smtpClient.EnableSsl = true;

    using (MailMessage mail = new MailMessage())
    {
        mail.Subject = "subject";
        mail.From = new MailAddress("email", "name");
        mail.To.Add(new MailAddress("email"));
        mail.Body = "body";
        mail.IsBodyHtml = true;

        smtpClient.Send(mail);
    }  
}

am i doing it right using 2 using statements or only the first using statement is necessary?

thanks

Answer 1

There is nothing inherently wrong with having multiple using statements. It keeps the lifetime of objects to the minimum which is not a bad thing to do.

Answer 2

When nesting using statements, it's more idiomatic to do it without indentation:

using (SmtpClient smtpClient = new SmtpClient("xxx", 587))
using (MailMessage mail = new MailMessage())
{
    smtpClient.Credentials = new System.Net.NetworkCredential("email", "pass");
    smtpClient.EnableSsl = true;

    mail.Subject = "subject";
    mail.From = new MailAddress("email", "name");
    mail.To.Add(new MailAddress("email"));
    mail.Body = "body";
    mail.IsBodyHtml = true;

    smtpClient.Send(mail);
}

This isn't always possible, because you sometimes need to do some processing between the first and the second using . It works in your example, though.