LINQ: Using INNER JOIN, Group and SUM

Question

I am trying to perform the following SQL using LINQ and the closest I got was doing cross joins and sum calculations. I know there has to be a better way to write it so I am

Answer 1

For me (using 4.0), the following works.

var total = from T1 in context.T1
            join T2 in context.T2 on T1.T2ID equals T2.T2ID
            join T3 in context.T3 on T2.T3ID equals T3.T3ID
            group T3 by new { T1.Column1, T1.Column2 } into g
            select new { 
                Column1 = g.Key.Column1, 
                Column2 = g.Key.Column2, 
                Amount = g.Sum(t3 => t3.Column1) 
            };