如何使用LINQ C過濾列表＃

Question

我需要將List<Students>過濾爲StudentsWitHighestDebts。

標準是隻有在ZachetDidNotPass有最大值的學生和maximum-1在所有List<Students>都包括在結果中。

var StudentsWitHighestDebts = students 
       .Where(s => s.ZachetDidNotPass.(some condition)) 
       .OrderBy(s => s.Name) 
       .ToList(); 

例如，假設有ZachetDidNotPass值0 1 2 5 6 7學生名單。由此產生的StudentsWitHighestDebts只應包含ZachetDidNotPass中7 and 6值的學生。

Answer 1

第一種選擇：取2最高債務和過濾學生通過ZachetDidNotPass：

var highestDebts = students.Select(s => s.ZachetDidNotPass) 
    .OrderByDescending(p => p).Take(2).ToArray(); 
var studentsWitHighestDebts = students 
    .Where(s => highestDebts.Contains(s.ZachetDidNotPass)) 
    .OrderByDescending(s => s.ZachetDidNotPass).ToList(); 

第二個方案 - 按ZachetDidNotPass，通過關鍵降序排序組，取前2組，然後從學生羣體

var studentsWitHighestDebts = students.GroupBy(s => s.ZachetDidNotPass) 
    .OrderByDescending(g => g.Key).Take(2) 
    .SelectMany(g => g).ToList(); 

而第三個選項（需要學生具有最高的債務和highestDebt - 1）

var highestDebt = students.Max(s => s.ZachetDidNotPass); 

var studentsWitHighestDebts = students 
    .Where(s => s.ZachetDidNotPass == highestDebt || s.ZachetDidNotPass == highestDebt - 1) 
    .OrderByDescending(s => s.ZachetDidNotPass).ToList();