Linq按日期获得数据组的总和
我的数据看起来像：
read_date | T1 | T2 | 15.02.2000 | 2 | 3 | 16.02.2000 | 4 | 5 | 15.03.2000 | 2 | 3 | 16.03.2000 | 5 | 4 | 我想获得T1和T2的总和，如下所示：
read_date | T1 | T2 | 02.2000 | 6 | 8 | 03.2000 | 7 | 7 |
我试着写这样的东西：
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) };
但这并没有给出预期的数据。是否有任何例子可以提供每小时数据，每日总和等数据。
谢谢
在分组时，您应该只考虑年份和月份：
var result = from s in meter_readings.Take(10) group s by new { date = new DateTime(s.read_date.Year, s.read_date.Month, 1) } into g select new { read_date = g.Key.date, T1 = g.Sum(x => x.T1), T2 = g.Sum(x => x.T2) };
首先，我认为你可以跳过匿名类型：
var result = from s in meter_readings.Take(10) group s by s.read_date into g select new { read_date = g.Key, T1 = g.Sum(x => x.T1), T2 = g.Sum(x => x.T2) };
其次，要按月分组，请使用一些唯一标识月份的值，如下所示：
var result = from s in meter_readings.Take(10) group s by s.read_date.ToString("yyyy.MM") into g select new { read_month = g.Key, T1 = g.Sum(x => x.T1), T2 = g.Sum(x => x.T2) };
您当前的分组将按完整日期分组（即15.02.2000而不是02.2000）。 这将最终为每一天创造一个单独的团体，而不是一个月。
通过（假设它是日期对象）将.Month添加到组中：
group s by new { s.read_date.Month} into g
static void Main() { var list = new List { new meter_reading {Date = new DateTime(2000, 2, 15), T1 = 2, T2 = 3}, new meter_reading {Date = new DateTime(2000, 2, 10), T1 = 4, T2 = 5}, new meter_reading {Date = new DateTime(2000, 3, 15), T1 = 2, T2 = 3}, new meter_reading {Date = new DateTime(2000, 3, 15), T1 = 5, T2 = 4} }; var sum = list .GroupBy(x => GetFirstDayInMonth(x.Date)) .Select(item => new meter_reading { Date = item.Key, T1 = item.Sum(x => x.T1), T2 = item.Sum(x => x.T2), }).ToList(); } private static DateTime GetFirstDayInMonth(DateTime dateTime) { return new DateTime(dateTime.Date.Year, dateTime.Date.Month, 1); }
query.OrderBy(o => o.OrderDate) .GroupBy(o => DbFunctions.CreateDateTime(o.OrderDate.Year, o.OrderDate.Month, 1, 0, 0, 0)) .Select(group => new DateIncomeDto { Date = group.Key.Value, Income = group.Sum(item => item.PayFee ?? 0) });
它对我有用！