Multi parameter query

Question

Hi

I have table containing measurements like below:

Row   Date                                  Addr   Channel_O  
1        2011-02-27 15:21:58.830   A        1  
2        2011-02-27 09:06:30.697   A        1                
3        2011-02-26 22:59:57.060   A        0
4        2011-02-26 22:59:53.160   A        0
5        2011-02-26 20:48:32.720   A        1
6        2011-02-27 15:21:24.890   B        1
7        2011-02-27 07:42:31.300   B        1
8        2011-02-26 22:10:25.943   B        0
9        2011-02-26 20:48:32.933   B        1

I want to get the newest measurement from Addr A and B in my output (here row number 1 and 6).

I have tried this:

var deviceCount = owdc.OneWireLevelDevices.Count();

return owdc.OneWirelevelMeasurements.OrderByDescending(a => a.Addr).ThenByDescending(d => d.Date).Take(deviceCount);

But this gives me row number 1 and 2.

Can somebody help ?

Answer 1

perhaps make 2 Linq queries, one that only takes rows for Addr='A' and one that take rows for Addr='B', then use the 'Max' operator to take the row with the highest date.

something like this:

var Results1 = owdc.OneWireLevelMeasurements.Where(p => p.Addr == 'A').Max(p => p.Date);

var Results1 = owdc.OneWireLevelMeasurements.Where(p => p.Addr == 'B').Max(p => p.Date);

then combine these results in an IEnumerable or List collection.

Answer 2

I combined the two IEnumerable this way:

var combinedResult = Results1.Concat(Results2);