c# - 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 turning to the stack team for help.

SELECT T1.Column1, T1.Column2, SUM(T3.Column1) AS Amount
FROM T1
     INNER JOIN T2
        ON T1.T1ID = T2.T1ID
     INNER JOIN T3
        ON T2.T3ID = T3.T3ID
GROUP BY T1.Column1, T1.Column2

What I have been trying is the following LINQ code

var qTotal = from T2 in context.T2
             from T3 in context.T3
             where T3.T3ID == T3.T3ID
             group T3 by T2.T1ID into gT2T3
                  from T1 in context.T1
                  where gT2T3.Key.Equals(T1.T1ID)
                  select new { T1.Column1,T1.Column2,Amount = gT2T3.Sum(t => t.Column1)};

I know there has to be a better way to write it, I just do not know how, any help would be great!

Answer 1

Try this:

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 = T1.Column1, 
                Column2 = T2.Column2, 
                Amount = g.Sum(t3 => t3.Column1) 
            };