LINQ query using Group By and Let - asp.net

Question

I have the below table,
Name Consumed
A Flavour 1
B Flavour 2
C Flavour 1
C Flavour 3
A Flavour 3
B Flavour 1
C Flavour 3
A Flavour 2
A Flavour 1
C Flavour 1
A Flavour 1
B Flavour 2
Where in the first column I have the name of the persons and in the second column the Flavour preferred by them. I want to generate the below table, with Flavours as columns and find the sum of the Flavours preferred by each person. I know the solution to these using SQL, however I'm looking for a solution using LINQ VB.Net.
Name Flavour 1 Flavour 2 Flavour 3
A 3 1 1
B 1 2 0
C 2 0 2
SQL Query for achieving the above result,
SELECT Name,
SUM(CASE WHEN Consumed='Flavour 1' THEN 1 ELSE 0) AS Flavour 1,
SUM(CASE WHEN Consumed='Flavour 2' THEN 1 ELSE 0) AS Flavour 2,
SUM(CASE WHEN Consumed='Flavour 3' THEN 1 ELSE 0) AS Flavour 3
GROUP BY Name
Below is the LINQ query,
Dim query = (From row In dtMain.AsEnumerable
Let Flavour_1 = IIf(row.Field(Of String)("Consumed") = "1", 1, 0)
Let Flavour_2 = IIf(row.Field(Of String)("Consumed") = "2", 1, 0)
Let Flavour_3 = IIf(row.Field(Of String)("Consumed") = "3", 1, 0)
Group row By Code = row.Field(Of String)("Name")
Into freq = Group Select .Code = Code, .Count = freq.Count()).ToList
My difficulty is in how to aggregate the temporary variables Flavour_1, Flavour_2 and Flavour_3 using SUM function and group it by Name.

Answer 1

Given the following data:
Dim table = {
New With { .Name = "A", .Consumed = "Flavor 1" },
New With { .Name = "B", .Consumed = "Flavor 2" },
New With { .Name = "C", .Consumed = "Flavor 1" },
New With { .Name = "C", .Consumed = "Flavor 3" },
New With { .Name = "A", .Consumed = "Flavor 3" },
New With { .Name = "B", .Consumed = "Flavor 1" },
New With { .Name = "C", .Consumed = "Flavor 3" },
New With { .Name = "A", .Consumed = "Flavor 2" },
New With { .Name = "A", .Consumed = "Flavor 1" },
New With { .Name = "C", .Consumed = "Flavor 1" },
New With { .Name = "A", .Consumed = "Flavor 1" },
New With { .Name = "B", .Consumed = "Flavor 2" }
}
the query you're looking for is:
Dim result = From e In table
Group e By Name = e.Name Into g = group
Select New With
{
.Name = Name,
.Flavour1 = g.Count(Function(x) x.Consumed = "Flavor 1"),
.Flavour2 = g.Count(Function(x) x.Consumed = "Flavor 2"),
.Flavour3 = g.Count(Function(x) x.Consumed = "Flavor 3")
}
It's quite similar to your SQL (group, then aggregate), but you use Count instead of SUM.
You don't need a Let.