AX2012 LINQ - How to compare datetime

hi everyone,

I'm newbie with the AX.

I'm using LinQ to get data from AX server.

Here are my codes:

 QueryCollection<ContactPerson> contact = new QueryCollection<ContactPerson>(provider);

var results2 = (from c in contact 
where c.ModifiedDateTime >= fromDate

with ModifiedDateTime is ValueType type.

 I also tried to use  the command Convert.ToDateTime( c.ModifiedDateTime) >= fromDate but it didn't work too.

Please help me to solve this problem.

Thank you very much.