to send to multiple recipients, separate  recipient string with a comma as separator and later call the Send method.

string recipient = "foo@bar.com,foo2@bar.com,foo3@bar.com";
Then to add the recipients to the MailMessage object:

string[] emailTo = recipient.Split(',');
for (int i = 0; i < emailTo.GetLength(0); i++)
    mailMessageObject.To.Add(emailTo[i]);

问候，

Praveen Nelge

Regards,
Praveen Nelge