Linq get sum of data group by date
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my data look like:

     read_date |  T1  |  T2  |
    15.02.2000 |   2  |   3  |
    16.02.2000 |   4  |   5  |
    15.03.2000 |   2  |   3  |
    16.03.2000 |   5  |   4  |

I want to get mountly sum of T1 and T2, like this:

     read_date |  T1  |  T2  |
       02.2000 |   6  |   8  |
       03.2000 |   7  |   7  |   

I try to write something like this:

    var result = from s in meter_readings.Take(10)
                 group s by new { s.read_date} into g
                 select new
                 {
                     read_date = g.Key.read_date,
                     T1 = g.Sum(x => x.T1),
                     T2 = g.Sum(x => x.T2)
                 };

but this does not give expected data.Is there any example to give data hourly sums, daily sums, etc.

Thanks