Send an Email with attachment to Multiple Recipients using ASP.Net

Get all email address to list from Database. Here I am using LINQ to SQL to get Email Address from Database.

DBDataContext DB = new DBDataContext();

string KitName = rdoAffectedKit.SelectedItem.Text.ToString();

var query = from p in DB.KitMembers
where p.KitID == (from kit in DB.Kits
where kit.KitName == KitName
select kit.KitID).First()
select p;

List _emailList = new List();
foreach (var obj in query)
_emailList.Add(obj.MemberEmail);
//MemberEmail is the DB filed, which holds the email address

SendEmail(_emailList);
//Send Email is the method, which sends email to all recipients


protected void SendEmail(List _Recipients)
{
MailMessage message = new MailMessage();

//Add All Recipients Address to Mail Message
foreach(string _toAddress in _Recipients)
message.To.Add(new MailAddress(_toAddress));

message.From = new MailAddress(ConfigurationManager.AppSettings ["From"].ToString());
message.Subject = ConfigurationManager.AppSettings["Subject"].ToString();
message.Body = ConfigurationManager.AppSettings["Body"].ToString();

//SMTP Server Configuration
string SMTPPort = ConfigurationManager.AppSettings["Port"].ToString();
string SMTPServer = ConfigurationManager.AppSettings["SMTPServer"].ToString();
SmtpClient client = new SmtpClient(SMTPServer, Convert.ToInt32(SMTPPort));
client.Credentials = CredentialCache.DefaultNetworkCredentials;

//Attach Xls Template
string source = Server.MapPath("ECRTest.xlsm");
Attachment data = new Attachment(source);
message.Attachments.Add(data);

try
{
//Sends an Email to Recipients
client.Send(message);
Response.Write("An E-Mail has been sent");
}
catch
{
Response.Write("Error: Mail has not been sent");
}
}

I have maintained From Address, Subject, Body, SMTPServer and Port maintained in Web.Config File.