How to compare and sum values of multiple periods using LINQ in VB.Net - vb.net

Question

I have the following example datatable:
Value1 Value2 Customer Product Date
100 50 1000 100 1.8.2010
50 20 1000 101 5.1.2010
200 60 1000 100 6.2.2011
180 100 1001 100 7.3.2010
500 700 1000 100 1.1.2010
300 300 1001 100 4.4.2011
250 600 1000 100 3.3.2011
And now the user should be able to compare multiple periods. In this example the user chose two periods: 1.1.2010 - 31.12.2010 and 1.1.2011 - 31.12.2011. The result of the example should be:
Customer Product SumValue1Period1 SumValue2Period1 SumValue1Period2 SumValue2Period2
1000 100 600 750 450 660
1000 101 50 20 0 0
1001 100 300 100 300 300
How can I do this?

Answer 1

Since you have known number of columns, you can group data by Customer and products and then take conditional sum from grouping and it will make different columns of the resultant query.
Please have a look at following LinqPad program. Sorry, I'm not familiar with VB.Net so I have coded it in C#, but you'll get the fair idea:
void Main()
{
var Period1Start = new DateTime(2010,1,1);
var Period1End = new DateTime(2010,12,31);
var Period2Start = new DateTime(2011,1,1);
var Period2End = new DateTime(2011,12,31);
List<Item> lst = new List<Item>
{
new Item{ Value1 = 100, Value2 = 50, Customer = 1000, Product = 100 , Date = new DateTime(2010,8,1)},
new Item{ Value1 = 50, Value2 = 20, Customer = 1000, Product = 101 , Date = new DateTime(2010,5,1)},
new Item{ Value1 = 200, Value2 = 60, Customer = 1000, Product = 100 , Date = new DateTime(2011,2,6)},
new Item{ Value1 = 180, Value2 = 100, Customer = 1001, Product = 100 , Date = new DateTime(2010,7,3)},
new Item{ Value1 = 500, Value2 = 700, Customer = 1000, Product = 100 , Date = new DateTime(2010,1,1)},
new Item{ Value1 = 300, Value2 = 300, Customer = 1001, Product = 100 , Date = new DateTime(2011,4,4)},
new Item{ Value1 = 250, Value2 = 600, Customer = 1000, Product = 100 , Date = new DateTime(2011,3,3)}
};
var grp = lst.GroupBy(x=>new{x.Customer, x.Product}).
Select(y=> new
{
Customer = y.Key.Customer,
Product = y.Key.Product,
SumValue1Period1 = y.Where(x=>x.Date >= Period1Start && x.Date<= Period1End).Sum(p=>p.Value1),
SumValue2Period1 = y.Where(x=>x.Date >= Period1Start && x.Date<= Period1End).Sum(p=>p.Value2),
SumValue1Period2 = y.Where(x=>x.Date >= Period2Start && x.Date<= Period2End).Sum(p=>p.Value1),
SumValue2Period2 = y.Where(x=>x.Date >= Period2Start && x.Date<= Period2End).Sum(p=>p.Value2)
});
Console.WriteLine(grp);
}
// Define other methods and classes here
public class Item
{
public int Value1{get;set;}
public int Value2{get;set;}
public int Customer{get;set;}
public int Product{get;set;}
public DateTime Date{get;set;}
}

Answer 2

Take a look at
http://msdn.microsoft.com/en-us/vbasic/bb737908
Specifically, the 'GroupBy - Nested' example. It shows using LINQ to group by 'customer's orders, first by year, and then by month.' You situation should be more straight forward since it's just the date range.