The type of one of the expressions in the join clause is incorrect. Type inference failed in the cal

I Had written the LinQ query then, it is showing error at join as below:
The type of one of the expressions in the join clause is incorrect. Type inference failed in the call to 'Join'.

List<AlertInfo> AlertInfos = new List<AlertMaster>();
List<DataBusiness> dataBusiness = new List<DataMessage>();

List<BusinessTableInformation> Alertlist = (from a in AlertInfos
join m in dataBusiness // Here error is showing
on a.AlertId equals m.AlertId
where a.SendEmail == true && m.Mode == true && m.MailSent == null && m.Type == 1
select new BusinessTableInformation
{
UserId = m.UserId,
AlertId = m.AlertId,
BusinessId = m.BusinessId,
EmailNote = a.EmailNote,
StatusId = a.Status.StatusId
}).ToList<BusinessTableInformation>();


please help me.....