Linq Error

Question

I get this error for the linq below.

Error: at least one object must implement icomparable

var minDate1 = (from c in DataAccess.VolunteerHistoryDataSet.Tables[0].AsEnumerable()
                                where c["ServiceDateStart"] != DBNull.Value
                                orderby c["ServiceID"], c["ServiceDateStart"]
                                select new
                                {
                                    Date = Convert.ToDateTime(c["ServiceDateStart"])
                                }).ToList().Min();

Vulpes · Answer

The problem appears to be that c[ServiceID] and c[ServiceDateStart] both return a System.Object which doesn't implement IComparable and so cannot be ordered. You'll therefore need to convert them to their actual types - I'd imagine Int32 and DateTime - which do implement IComparable. So I'd try: var minDate1 = (from c in DataAccess.VolunteerHistoryDataSet.Tables[0].AsEnumerable() where c[ServiceDateStart] != DBNull.Value orderby Convert.ToInt32(c[ServiceID]) Convert.ToDateTime(c[ServiceDateStart]) select Convert.ToDateTime(c[ServiceDateStart])).Min();