实体框架，按日期/周/月分组

Question

正如标题所说，我的表中有一个日期时间列。

在三种不同的情况下，我需要以三种方式按我的记录进行分组：

1. 按天分组
2. 按周分组
3. 按月分组

如果可能的话，我如何在实体框架中使用 lambda 表达式执行这 3 种不同的分组语句？

更新：链接的问题是重复的，不是真正的重复。我要的是 lambda 解决方案，但链接中没有它

Answer 1

你可以使用这个方法：

var ByDayGrouped = new TestEntities().Objects.GroupBy(O => new { O.date.Year, O.date.Month, O.date.Day }).ToList();

var ByMonthGrouped = new TestEntities().Objects.GroupBy(O => new { O.date.Year, O.date.Month }).ToList();

var ByWeekGrouped = new TestEntities().Objects.GroupBy(O => (O.date.DayOfYear % 7) + M ).ToList();

Answer 2

使用这个

List<MyEntitiy> list = (from e in Context.MyEntities group e by e.Date.Day into g select g).ToList();

对于月份，将 e.Date.Day 替换为 e.Date.Month

对于Week，您必须首先Calculate WeekOfYear

public int GetWeekOfYear(this DateTime d)
{
    GregorianCalendar c = new  GregorianCalendar();
    return c.GetWeekOfYear(d,CalenderWeekRule.FirstDay,DayOfWeek.Sunday);
}

并使用

List<MyEntitiy> list = (from e in Context.MyEntities group e by e.Date.GetWeekOfYear() into g select g).ToList();

Answer 3

您可以使用以下格式使用 linq 和 lambda 表达式

按天分组

    var results = from p in db.table
                          group p.data by p.DateTime.UtcNow.Day into g
                          select new { Id = g.Key, parameters = g };

按周分组

    var result = from p in db.table
                         group p.data by p.DateTime.UtcNow.DayOfWeek into g
                          select new { Id = g.Key, parameters = g}

否则

    //get the 7days of the week by the below method and perform between operation
    DateTime fromDate = DateTime.Today.Subtract(new TimeSpan(7, 0, 0, 0));
    DateTime today = DateTime.Today;
    var result = from p in db.table
                         group p.data by (DbFunctions.TruncateTime(today) && DbFunctions.TruncateTime(today) >= DbFunctions.TruncateTime(fromDate)) into g
                         select new { Id = g.Key, parameters = g}

月份类似

    DateTime fromDate = DateTime.Today.Subtract(new TimeSpan(30, 0, 0, 0));
    DateTime today = DateTime.Today;
    var result = from p in db.table
                         group p.data by (DbFunctions.TruncateTime(today) && DbFunctions.TruncateTime(today) >= DbFunctions.TruncateTime(fromDate)) into g
                         select new { Id = g.Key, parameters = g}