Is it possible to Pivot data using LINQ?

Question

I am wondering if it is possible to use LINQ to pivot data from the following layout:

CustID | OrderDate | Qty
1      | 1/1/2008  | 100
2      | 1/2/2008  | 200
1      | 2/2/2008  | 350
2      | 2/28/2008 | 221
1      | 3/12/2008 | 250
2      | 3/15/2008 | 2150

into something like this:

CustID  | Jan- 2008 | Feb- 2008 | Mar - 2008 |
1       | 100       | 350       |  250
2       | 200       | 221       | 2150

Answer 1

Something like this?

List<CustData> myList = GetCustData();

var query = myList
    .GroupBy(c => c.CustId)
    .Select(g => new {
        CustId = g.Key,
        Jan = g.Where(c => c.OrderDate.Month == 1).Sum(c => c.Qty),
        Feb = g.Where(c => c.OrderDate.Month == 2).Sum(c => c.Qty),
        March = g.Where(c => c.OrderDate.Month == 3).Sum(c => c.Qty)
    });

GroupBy in Linq does not work the same as SQL. In SQL, you get the key and aggregates (row/column shape). In Linq, you get the key and any elements as children of the key (hierarchical shape). To pivot, you must project the hierarchy back into a row/column form of your choosing.