Linq：按日期间隔分组（5、10、15 等.. 年）

Question

我有一个 MVC/ASP.NET Web 应用程序，用于跟踪员工信息，例如 StartDate，它是一个 DateTime 数据类型，表示特定员工在公司开始工作的时间。

我们还为在公司工作的员工颁发奖励，并希望按在公司工作 5、10、15、20、25、30 年以上的时间分组。

我如何编写一个 Linq 语句，该语句仅按在公司的时间已达到将收到“在公司的时间”奖？感谢您的帮助。

Answer 1

这个解决方案做得很好！使用您的解决方案，我采用了您的主要逻辑并进行了一些更改，这些更改足以使我认为其他人可能会从中受益。凭借您在帮助方面的耐心以及您对我试图完成的工作的专业知识，绝对无法做到这一点。

请参阅下面的更改...

控制器

public ActionResult LengthOfService()
{
    ViewBag.Title = "Length of Service Awards Report";
    var people = db.People.ToList().Where(p => !p.EndDate.HasValue);
    var now = DateTime.Today;
    var period = 5;
    var maxPeriod = 30;
    var query = (from p in people
                let interval = DateTime.MinValue.AddDays((now - p.LengthOfService).TotalDays).Year / period
                where interval > 0
                group p by Math.Min(interval * period, maxPeriod) into x
                orderby x.Key
                select new AwardInfo
                {
                    Years = x.Key,
                    People = x
                }).ToList(); 
    return View(query);
}

查看模型

public class AwardInfo
{
    public int Years { get; set; }
    public IEnumerable<People> People { get; set; }
}

查看

@model List<CPR.Models.AwardInfo>

<h2>@ViewBag.Title</h2>

<table class="table table-responsive table-hover">
    <thead>
        <tr>

            <th class="col-sm-1">Service Award</th>
            <th class="col-sm-2">Name</th>
            <th class="col-sm-2">Date of Service</th>
            <th class="col-sm-2">Company</th>
        </tr>
    </thead>
    @foreach (var item in Model)
    {
        <tbody>
            <tr>
                <th class="panel-bg" colspan="5">@item.Years years</th>
            </tr>
        </tbody>
        <tbody>
            @foreach (var person in item.People)
            {
                <tr>
                    <td class="col-sm-1"></td>
                    <td class="col-sm-2">@person.LastName, @person.FirstName</td>
                    <td class="col-sm-2">@person.LengthOfService.ToShortDateString()</td>
                    <td class="col-sm-2">@person.Companies.Name</td>
                </tr>
            }
        </tbody>
    }
</table>

Answer 2

查看以下用于演示如何按周期/间隔分组的单元测试。

[TestClass]
public class GroupByDateIntervalsTests {
    [TestMethod]
    public void Group_By_5_year_Intervals_Max_30() {
        var employees = GenerateRandomDates(DateTime.Now, 5, 40, 50).Select((d, i) => new { id = i, StartDate = d });

        var now = DateTime.Today;
        var period = 5;
        var maxPeriod = 30;
        var groups = from employee in employees
                     let interval = DateTime.MinValue.AddDays((now - employee.StartDate).TotalDays).Year / period
                     group employee by Math.Min(interval * period, maxPeriod) into g
                     orderby g.Key
                     select new {
                         period = g.Key,
                         employees = g.Select(e => e.id).ToArray()
                     };

        var result = groups.ToList();
    }

    [TestMethod]
    public void Group_By_Random_Interval_Max_30() {
        var employees = GenerateRandomDates(DateTime.Now, 5, 40, 50).Select((d, i) => new { id = i, StartDate = d });

        var now = DateTime.Today;
        var periods = new[] { 5, 10, 20, 30 };
        var groups = employees
            .GroupBy(employee => {
                var period = DateTime.MinValue.AddDays((now - employee.StartDate).TotalDays).Year;
                var interval = periods.Where(p => (period / p) > 0).Max();
                return Math.Min(interval, periods.Max());
            })
            .Select(g => new {
                period = g.Key,
                employees = g.Select(e => e.id).ToArray()
            });

        var result = groups.ToList();
    }

    public List<DateTime> GenerateRandomDates(DateTime rootDate, int minAgeAtRootDate, int maxAgeAtRootDate, int count) {
        Contract.Assert(minAgeAtRootDate <= maxAgeAtRootDate, "invalid age range. Minimum age cannot be higher than maximum age");
        var minDate = rootDate.Date.AddYears(-maxAgeAtRootDate);
        var maxDate = rootDate.Date.AddYears(-minAgeAtRootDate);
        var range = (maxDate - minDate).Days;
        if (range == 0) {
            range = 364;
        }
        var random = new Random();
        var dates = Enumerable
            .Range(1, count)
            .Select(i => minDate.AddDays(random.Next(range)))
            .ToList();
        return dates;
    }
}