function IsMail(mail) 
{ 
    var patrn = /^w+([-+.]w+)*@w+([-.]w+)*.w+([-.]w+)*$/; 
    return patrn.test(mail);
}

------解决方案--------------------
C# code

/// <summary>
        /// Email 格式是否合法
        /// </summary>
        /// <param name="StrEmail">源字符串</param>
        public static bool IsEmail(string StrEmail)
        {
            return Regex.IsMatch(StrEmail, @"^\w+((-\w+)|(\.\w+))*\@[A-Za-z0-9]+((\.|-)[A-Za-z0-9]+)*\.[A-Za-z0-9]+$");
        }

------解决方案--------------------
string mailAddress  = "adsfasfd";
try
{
   MailAddress temp = new MailAddress(mailAddress);
}
catch(Execption ex)
{
    //邮件地址不规范
}

------解决方案--------------------
探讨

C# code
/// <summary>
        /// Email 格式是否合法
        /// </summary>
        /// <param name="StrEmail">源字符串</param>
        public static bool IsEmail(string StrEmail)
        {
            return Regex.IsMatch(StrEmail, @"^\w+((-\w+)|(\.\w+))*\@[A-Za-z0-9]+((\.|-)[A-Za-z0-9]+)*\.[A-Za-z0-9]+$");
        }