如何使用LINQ C过滤列表＃

Question

我需要将List<Students>过滤为StudentsWitHighestDebts。

标准是只有在ZachetDidNotPass有最大值的学生和maximum-1在所有List<Students>都包括在结果中。

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

例如，假设有ZachetDidNotPass值0 1 2 5 6 7学生名单。由此产生的StudentsWitHighestDebts只应包含ZachetDidNotPass中7 and 6值的学生。

Answer 1

第一种选择：取2最高债务和过滤学生通过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(); 

第二个方案 - 按ZachetDidNotPass，通过关键降序排序组，取前2组，然后从学生群体

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

而第三个选项（需要学生具有最高的债务和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();