LINQ Group by with VB.net

I am having an issue figuring out how to pull out only one record whre the old_startdt, loc, and gamedaynbr are the same. 
Can someone help me?  I am trying to do this with a lambda expression if at all possible. If not a linq expression would work.
Here is my columns on how I am ordering by for now:
tblPostQuery = tblPostQuery.OrderBy(Function(o As TablePostDTO) o.Old_StartDateDt) _ .ThenBy(Function(o As TablePostDTO) o.Loc) _ .ThenBy(Function(o As TablePostDTO) o.Old_GameDayNbr) _ .ToL