Linq Group By - linq

Question

I have a abstract Class where a Recipient either can be a EMailRecipient or a SMSRecipients.
Im selecting the data out in a List like List<Recipient>. For statistic reason i need to know then number of recipients based on the CountryCode in the SMSRecipient and i thought i could do that in linq. But i cant seem to cast a Recipient as a SMSRecipient like
var q = from v in AMessageQueueContentList
group v by (FlexyNet.Data.SMSRecipient)v.Recipient into g
select count(g);
My class looks like this:
public abstract class Recipient
{
public int MemberID { get;set;}
public Recipient(){}
}
public class EMailRecipient : Recipient
{
public string EMail { get; set; }
public bool ValidMail { get; set; }
public EMailRecipient(FlexyDataReader read)
{
this.MemberID = (int)read["MemberID"];
this.EMail = (string)read["Recipient"];
}
public EMailRecipient(int memberID,string eMail)
{
this.MemberID = memberID;
this.EMail = (string)eMail;
}
}
public class SMSRecipient : Recipient
{
public string Number { get; set; }
public string CountryCode { get; set; }
public nimta.Recipient NimtaRecipient { get; set; }
}

Answer 1

Could you do something like this?
var counts = from m in AMessageQueueContentList
let s = m.Recipient as FlexyNet.Data.SMSRecipient
where s != null
group s by s.CountryCode into g
select new { CountryCode = g.Key, Count = g.Count() };
Or if you actually have a list of Recipient objects, you could use LINQ's OfType<T>() extension method:
var sms = recipients.OfType<FlexyNet.Data.SMSRecipient>();
var counts = from s in sms
group s by s.CountryCode into g
select new { CountryCode = g.Key, Count = g.Count() };