Method to get a summary view from a dataset - linq

Question

I have a dataset that looks like this:
Date
Category
Rate
Quantity
There will be 0 or 1 row for each Category for any given Date.
What is a good way to get this data into a summary type of view?
For example:
Date
Category1_Rate
Category2_Rate
Category3_Rate
Category4_Rate
I have a fixed number of Categories.
I'm using linq.
Here is an example. If I have this data:
Date Category Rate Quantity
1/1/12 toys 15 12
1/1/12 games 20 20
1/1/12 dvds 18 30
1/2/12 toys 19 13
1/2/12 dvds 20 17
I want to produce a summary that looks like this:
Date toys_rate games_rate dvds_rate
1/1/12 15 20 18
1/2/12 19 null 20

Answer 1

Possibly something like this
var summarydata =
from r in table
group r by r.Date into g
select new
{
Date = g.Key,
ToysRate = g.Where(e=> e.Category == "toys").Count() > 0 ?
(int?)g.Where(e=> e.Category == "toys").First().Rate : null,
GamesRate = g.Where(e=> e.Category == "games").Count() > 0 ?
(int?)g.Where(e=> e.Category == "games").First().Rate : null,
DvdsRate = g.Where(e=> e.Category == "dvds").Count() > 0 ?
(int?)g.Where(e=> e.Category == "dvds").First().Rate : null
};
Note I haven't tested this as I don't current have access to a C# environment.
EDIT - Added nullable int casts to properly set the type of the various rate fields in the resulting anonymous type.