Linq query with GROUP BY on multiple fields, SUM and COUNT - vb.net

Question

I'm trying to use a LINQ SQL to query my database.
Let's say I have some data that looks like this:
var1 var2 var3 qty
1 a 1a 50
1 a 1a 25
2 b 2b 10
2 b 2b 15
2 b 2b 10
3 a 3a 25
I know how to format my query in SQL. It would be something like this:
SELECT var1, var2, var3, count(*) AS count, sum(qty) As quantity
FROM MyTable
GROUP BY var1, var2, var3
In this case the output would be something like this:
var1 var2 var3 Count Qty
1 a 1a 2 75
2 b 2b 3 35
3 a 3a 1 25
How can I do the same thing with LINQ in vb.net
Dim groups = From j In MyTable
Group By j.var1, j.var2, j.var3 Into g
Select new {var1 = g.var1,
var2 = g.var2,
var3 = g.var3,
quantity = sum(g.qty),
count = count(*)}
That's not quite right, but I think it's close. I don't understand the syntax of the group by in VB.NET.

Answer 1

You want to group by an anonymous type, this is the syntax in VB.NET (note the Key):
Dim groups =
From j In MyTable
Group By x = New With {Key .var1 = j.var1, Key .var2 = j.var2, Key .var3 = j.var3} Into g = Group
Select New With {
.var1 = x.var1,
.var2 = x.var2,
.var3 = x.var3,
.quantity = g.Sum(Function(r) r.qty),
.count = g.Count()
}

Answer 2

You will have to use anonymous type like this:-
Group j By Key = New With { Key .Var1 = j.var1,
Key .Var2 = j.var2,
Key .Var3 = j.var3 } Into Group
Select New With { .var1 = Key.Var1,
.var2 = Key.Var2,
.var3 = Key.Var3,
.quantity = Group.Sum(Function(x) x.qty),
.count = Group.Count()
}