LINQ tip: How to Implement group nesting by calling GroupBy multiple times

[Csharp]
Using System;
Using System. Linq;
 
Namespace ConsoleApplication1
{
Class Program
{
Public class S
{
Public int Year;
Public int Month;
Public int Day;
}

Static void Main (string [] args)
{
Var m = new [] {
New S {Year = 2000, Month = 1, Day = 10 },
New S {Year = 2000, Month = 2, Day = 10 },
New S {Year = 2010, Month = 1, Day = 1 },
New S {Year = 2010, Month = 2, Day = 1 },
New S {Year = 2010, Month = 1, Day = 2 },
New S {Year = 2010, Month = 2, Day = 2 },
New S {Year = 2000, Month = 1, Day = 2 },
New S {Year = 2000, Month = 2, Day = 2 },
};
 
Var q2 =
From s in m
Group s by s. Year into YearGroup
Select new
{
Year = YearGroup. Key,
MonthGroups =
From s2 in YearGroup
Group s2 by s2.Month into MonthGroup
Select new
{
Month = MonthGroup. Key,
Days =
From s3 in MonthGroup
Orderby s3.Day
Select s3.Day
}
};
 
 
Var q = m. GroupBy (
S => s. Year,
(Year, YearGroup) => new
{
Year,
MonthGroups =
YearGroup. GroupBy (
S2 => s2.Month,
(Month, MonthGroup) => new
{
Month,
Days = MonthGroup. OrderBy (s3 => s3.Day). Select (s3 => s3.Day)
}
)
}
);
 
Foreach (var elem in q)
// Foreach (var elem in q2)
{
Console. WriteLine ("Year = {0}", elem. Year );
Foreach (var elem2 in elem. MonthGroups)
{
Console. WriteLine ("\ tMonth = {0}", elem2.Month );
Foreach (var day in elem2.Days)
Console. WriteLine ("\ t \ tDay = {0}", day );
} Www.2cto.com
}
}
}
}
// Year = 2000
// Month = 1
// Day = 2
// Day = 10
// Month = 2
// Day = 2
// Day = 10
// Year = 2010
// Month = 1
// Day = 1
// Day = 2
// Month = 2
// Day = 1
// Day = 2
Author: zwvista