Question

Here is a SQL query that I am trying to convert in to Linq. I am using a generic list of objects and not a DataTable if that is relevant.

Select Max(Date), ID, Property1, Peroperty2 From List Group By ID

Please help.

Answer 1

Though your SQL is not valid as Property1 and Property2 must be part of your aggregates, this will group by ID, Property1, then Property2 in that order which is what I believe you are looking for:

from obj in List
group obj by new {obj.ID, obj.Property1, obj.Property2 } into g
select new 
       { 
          ID = g.Key.ID, 
          Property1 = g.Key.Property1, 
          Property2 = g.Key.Property2,  
          MaxDate = g.Max(p => p.Date) 
       }

which is equivalent to :

Select Max(Date), ID, Property1, Peroperty2 
From List 
Group By ID, Property1, Property2