如何在 Entity Framework Core 中按周分组? [英] How to group by week in Entity Framework Core?

问题描述

在实体框架 6 中，我可以使用 SqlFunctions.DatePart() 方法:

In Entity Framework 6 I can use SqlFunctions.DatePart() method:

var byWeek = data.GroupBy(x => SqlFunctions.DatePart("week", x.Date));

但是这些类(DbFunctions 和 SqlFunctions 在 Entity Framework Core 中不可用)(参考).

But these classes (DbFunctions and SqlFunctions are not available in Entity Framework Core) (reference).

所以我的问题是如何在实体框架核心中按周分组?

推荐答案

我目前针对缺失功能的解决方法是

My current workaround for the missing functionality is

var firstMondayOfYear = this.GetFirstMondayOfYear(DateTime.Now.Year);
var entries =
    this.entitiesService.FindForLastMonths(this.CurrentUser.Id, 6)
        .GroupBy(x => ((int)(x.Date - firstMondayOfYear).TotalDays / 7))

函数GetFirstMondayOfYear:

private DateTime GetFirstMondayOfYear(int year)
{
    var dt = new DateTime(year, 1, 1);
    while (dt.DayOfWeek != DayOfWeek.Monday)
    {
        dt = dt.AddDays(1);
    }

    return dt;
}

这个分组给出了当年的周数和前几年的负值.

This grouping gives the week number for the current year and negative values for previous years.

稍后您可以使用此 getter 获取周名称:

Later you can get the week name by using this getter:

public string WeekName
{
    get
    {
        var year = DateTime.Now.AddYears((int)Math.Floor(this.WeekNumber / 52.0)).Year;
        var weekNumber = this.WeekNumber % 52;
        while (weekNumber < 0)
        {
            weekNumber += 52;
        }

        return $"{year}, W{weekNumber}";
    }
}

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