用日期字段周的IEnumerable列表C＃的LINQ或Lambda表达式组(C# Linq or

我试图做一个查询到IEnumerable<Object>按周进行分组，例如：

Project(Name, DateStart,ID)

我IEnumerable<Project> ，我希望做一个报告，按周分组。

对于〔实施例：

Week 1
 Project1  8/4/2013 ID1
 Project2  9/4/2013 ID2
Week 2
 Project1  16/4/2013 ID3
 Project2  18/4/2013 ID5
Week 3
 Project1  24/4/2013 ID7
 Project2  26/4/2013 ID8

请，如果有人能够给我一个手，我真的很感激！ 我试图做一个lambda表达式，但没有成功。

谢谢！

Answer 1:

var weekGroups = projects
    .Select(p => new 
    { 
        Project = p, 
        Year = p.DateStart.Year, 
        Week =  CultureInfo.InvariantCulture.Calendar.GetWeekOfYear
                      (p.DateStart, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday)
    })
    .GroupBy(x => new { x.Year, x.Week })
    .Select((g, i) => new 
    { 
        WeekGroup = g, 
        WeekNum = i + 1,
        Year = g.Key.Year,
        CalendarWeek = g.Key.Week
    });

foreach (var projGroup in weekGroups)
{
    Console.WriteLine("Week " + projGroup.WeekNum);
    foreach(var proj in projGroup.WeekGroup)
        Console.WriteLine("{0} {1} {2}", 
            proj.Project.Name, 
            proj.Project.DateStart.ToString("d"), 
            proj.Project.ID);
}

Answer 2:

您需要定义可确定一个日期是在一周的函数：

int GetWeek(DateTime date) { ... }

然后，LINQ查询组是：

IEnumerable<IGrouping<int, Project>> groupedProjects = 
         myListOfProjects.GroupBy(p => GetWeek(p.DateStart));

您可以遍历分组项目列表：

foreach (var weekGroup in groupedProjects)
{
    int week = weekGroup.Key;
    foreach (var project in weekGroup)
    {
        Console.WriteLine("Week " + week + " | Project: " + project.ID);
    }
}

Answer 3:

我认为要简化这一任务，您可以添加WeekNumber属性到项目类后，你可以很容易按WeekNumber财产填补它，当你创建项目的对象

Project(Name, DateStart,ID,WeekNumber)

Answer 4:

我认为只是一个简单的投影就足够了：

// we'll just use the existing settings on the box.
DateTimeFormatInfo dfi = DateTimeFormatInfo.CurrentInfo;
var cal = dfi.Calendar;

var Projects = GetProjectsFromSomewhere(); // assuming IEnumerable<Project>

int week = 1; // this *could* be changed and projected in the Select instead.
foreach (var wg in from p in Projects
    group p by cal.GetWeekOfYear(
        p.StartDate, dfi.CalendarWeekRule, dfi.FirstDayOfWeek))
{
    Console.WriteLine("Week {0}", week);

    foreach (var p in wg)
    {
        Console.WriteLine("    {0} {1} {2}", p.Name, p.StartDate, p.ID);
    }
    week++;
}

Answer 5:

您可以使用GetWeekOfMonth扩展张贴在这里 ：

然后像做：

        var groups = projects.GroupBy(p => p.Start.GetWeekOfMonth());

        foreach (var group in groups)
        {
            Console.WriteLine("Week {0}", group.Key);
            foreach (var project in group)
            {
                Console.WriteLine("\t{0} | {1:dd/MM/yyyy} | {2}", 
                     project.Name, project.Start, project.Id);
            }
        }

Answer 6:

除了Tim Schmelter's回答，您可以在该日期之前获得的第一天在本周的日期，然后组。

为了获得在一周的第一天的日期。 您可以使用此代码：

public static class DateTimeExtensions
{
    public static DateTime StartOfWeek(this DateTime dt, DayOfWeek startOfWeek)
    {
        int diff = dt.DayOfWeek - startOfWeek;
        if (diff < 0)
        {
            diff += 7;
        }
        return dt.AddDays(-1 * diff).Date;
    }
}

那么你可以通过这样的一周的第一天组：

var weekGroups = projects
    .Select(p => new 
    { 
        Project = p
    })
    .GroupBy(x => x.Project.DateStart.StartOfWeek(DayOfWeek.Monday))
    .Select((g, i) => new 
    { 
        WeekGroup = g, 
        WeekNum = i + 1
    });

foreach (var projGroup in weekGroups)
{
    Console.WriteLine("Week " + projGroup.WeekNum);
    foreach(var proj in projGroup.WeekGroup)
        Console.WriteLine("{0} {1} {2}", 
            proj.Project.Name, 
            proj.Project.DateStart.ToString("d"), 
            proj.Project.ID);
} 

文章来源: C# Linq or Lambda expression Group by Week IEnumerable list with date field