詞典日期和價值觀，在LINQ

Question

發現每年最大日值有一個這樣的名單：

01/01/2009, 120 
04/01/2009, 121 
30/12/2009, 520 
01/01/2010, 100 
04/01/2010, 101 
31/12/2010, 540 

我需要找到每一年，如最後一個值結果會是520,540？

Answer 1

var lastValues = records.OrderByDescending(r => r.Date) 
        .GroupBy(r => r.Date.Year) 
        .Select(g => g.First().Value); 

Answer 2

class Program 
{ 
    static void Main() 
    { 
     var list = new[] 
     { 
      new { Date = new DateTime(2009, 1, 1), Value = 120 }, 
      new { Date = new DateTime(2009, 4, 1), Value = 121 }, 
      new { Date = new DateTime(2009, 12, 30), Value = 520 }, 
      new { Date = new DateTime(2010, 1, 1), Value = 100 }, 
      new { Date = new DateTime(2009, 4, 1), Value = 101 }, 
      new { Date = new DateTime(2010, 12, 31), Value = 540 }, 
     }; 
     var result = list 
      .GroupBy(x => x.Date.Year) 
      .Select(g => new { Date = g.Key, MaxValue = g.Max(x => x.Value) }); 
     foreach (var item in result) 
     { 
      Console.WriteLine(item); 
     } 
    } 
}