ASP调用C#编写的DLL发送邮件

using System;   
using System.Net.Mail;   
using System.Text;   

namespace IMELS   
{   
    public class SendMail   
    {   
        public SendMail() { }   
   
         private string _to = string.Empty;   
   
         /// <summary>   
         /// 收件人地址，多个用“,”号隔开   
         /// </summary>   
         public string To   
         {   
             set { _to = value; }   
         }   
   
         private string _from = string.Empty;   
   
         /// <summary>   
         /// 发件人地址   
         /// </summary>   
         public string From   
         {   
             set { _from = value; }   
         }   
   
         private string _fromName = string.Empty;   
   
         /// <summary>   
         /// 发件人显示名称   
         /// </summary>   
         public string FromName   
         {   
             set { _fromName = value; }   
         }   
   
         private string _cc = string.Empty;   
   
         /// <summary>   
         /// 抄送，多个用“,”号隔开   
         /// </summary>   
         public string CC   
         {   
             set { _cc = value; }   
         }   
   
         private string _bcc = string.Empty;   
   
         /// <summary>   
         /// 密抄，多个用“,”号隔开   
         /// </summary>   
         public string BCC   
         {   
             set { _bcc = value; }   
         }   
   
         private string _charset = "GB2312";   
   
         /// <summary>   
         /// 邮件正文的编码   
         /// </summary>   
         public string Charset   
         {   
             set { _charset = value; }   
         }   
   
         private string _contentType = "html";   
         /// <summary>   
         /// 邮件格式(html or txt)   
         /// </summary>   
         public string ContentType   
         {   
             set { _contentType = value; }   
         }   
   
         private string _subject = string.Empty;   
         /// <summary>   
         /// 邮件标题   
         /// </summary>   
         public string Subject   
         {   
             set { _subject = value; }   
         }   
   
         private string _body = string.Empty;   
         /// <summary>   
         /// 邮件内容   
         /// </summary>   
         public string Body   
         {   
             set { _body = value; }   
         }   
   
         private string _smtp;   
         /// <summary>   
         /// SMTP服务器地址   
         /// </summary>   
         public string Smtp   
         {   
             set { _smtp = value; }   
         }   
   
         private string _username;   
         /// <summary>   
         /// SMTP用户名   
         /// </summary>   
         public string Username   
         {   
             set { _username = value; }   
         }   
         /// <summary>   
         /// SMTP密码   
         /// </summary>   
         private string _password;   
   
         public string Password   
         {   
             set { _password = value; }   
         }   
   
         private int _port = 25;   
         /// <summary>   
         /// SMTP商品   
         /// </summary>   
         public int Port   
         {   
             set { _port = value; }   
         }   
   
         /// <summary>   
         /// 发送   
         /// </summary>   
         public void Send()   
         {   
             MailAddress from = new MailAddress(_from, _fromName);   
             MailMessage message = new MailMessage();   
             message.From = from;   
                
             string[] toadd = _to.Split(',');   
             foreach (string _add in toadd)   
             {   
                 try 
                 {   
                     message.To.Add(new MailAddress(_add));   
                 }   
                 catch(Exception e)   
                 {   
                     _error += "To Address Error : " + e.Message + "(" + _add + ");";   
                 }   
             }   
   
             if (_cc != string.Empty)   
             {   
   
                 string[] ccadd = _cc.Split(',');   
   
                 foreach (string _add in ccadd)   
                 {   
                     try 
                     {   
                         message.CC.Add(new MailAddress(_add));   
                     }   
                     catch (Exception e)   
                     {   
                         _error += "CC Address Error : " + e.Message + "(" + _add + ");";   
                     }   
                 }   
             }   
             if (_bcc != string.Empty)   
             {   
                 string[] bccadd = _bcc.Split(',');   
   
                 foreach (string _add in bccadd)   
                 {   
                     try 
                     {   
                         message.Bcc.Add(new MailAddress(_add));   
                     }   
                     catch (Exception e)   
                     {   
                         _error += "BCC Address Error : " + e.Message + "(" + _add + ");";   
                     }   
                 }   
             }   
   
             message.Sender = from;   
             message.Subject = _subject;   
             message.Body = _body;   
   
             if (_contentType == "html" || _contentType == string.Empty)   
             {   
                 message.IsBodyHtml = true;   
             }   
             else 
             {   
                 message.IsBodyHtml = false;   
             }   
   
             message.BodyEncoding = Encoding.GetEncoding(_charset);   
             message.DeliveryNotificationOptions = DeliveryNotificationOptions.None;   
             SmtpClient __smtp = new SmtpClient();   
             __smtp.Host = _smtp;   
             __smtp.Port = _port;   
             __smtp.UseDefaultCredentials = false;   
             __smtp.Credentials = new System.Net.NetworkCredential(_username, _password);   
             __smtp.DeliveryMethod = SmtpDeliveryMethod.Network;   
             try 
             {   
                 __smtp.Send(message);   
             }   
             catch (SmtpException e)   
             {   
                 _error += "SMTP Error:" + e.Message + ";";   
             }   
                
         }   
   
         private string _error = string.Empty;   
         /// <summary>   
         /// 返回错误信息   
         /// </summary>   
         public string Error   
         {   
             get { return _error; }   
         }   
         /// <summary>   
         /// 清空错误信息   
         /// </summary>   
         public void ClearErr()   
         {   
             _error = string.Empty;   
         }   
     }   
}

(鼠标移到代码上去，在代码的顶部会出现四个图标，第一个是查看源代码，第二个是复制代码，第三个是打印代码，第四个是帮助)

说一下具体实现过程：

1、首先新建一个类库项目；打开项目属性页，在“应用程序”标签设置程序集名称为“IMELS”（当然，这个你可以设置为你喜欢的名字），输出类型为类库，如图：

 
点击“程序集信息”，勾选“使程序集COM可见”，如图：