C＃的LINQ或Lambda表達式組

Question

我想通過每週做一個查詢到IEnumerable<Object>到組，例如：

Project(Name, DateStart,ID) 

我有IEnumerable<Project>，我希望做一個報告，按周分組。

對於〔實施例：

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 

請，如果有人能夠給我一個手，我真的很感激！我試圖做一個lambda表達式，但沒有成功。

謝謝！

Answer 1

我認爲要簡化這一任務，你可以添加WeekNumber屬性到項目 級和後補它，當你創建項目的對象，你可以通過WeekNumber財產容易組

Project(Name, DateStart,ID,WeekNumber) 

Answer 2

您需要定義一個可確定日期是其中周功能：

int GetWeek(DateTime date) { ... } 

然後LINQ查詢到基團是：

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

您可以在分組項目列表迭代：

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

Answer 3

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 4

可以使用GetWeekOfMonth擴展發佈here：

，然後做一些事情，如：

 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 5

我認爲只需一個簡單的投影就足夠了：

// 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 6

除了Tim Schmelter's答案您可以通過日期得到的第一天的日期在本週再組。

獲取本週第一天的日期。 您可以使用此代碼：

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; 
    } 
} 

那麼你可以在本週這樣的第一次約會組：

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); 
}