如何在 LINQ 中包含基于条件的列表

Question

我有这个代码：

ClassroomList.Where(x => x.StudentList.Any(y => y.IsMale) == true);

此代码 returns ClassroomList 仅当 StudentList 中的所有学生 IsMale == true 但 returns none 如果至少有 1 IsMale == false.

我如何总是 return ClassroomList 只包含 IsMale == true.

的学生

这里是 ClassroomList 的 Class:

public partial class ClassroomList
{
    public ClassroomList(){}
    public list<Student> StudentList {get; set;}
}

这是学生 Class:

public partial class Student 
{
    public Student (){}
    public bool IsMale {get; set;}
}

这是预期输出的示例

Classroomlist Count |  Studentlist Count |  Male | Female | 
         2                    5              3       2       
         2                    10             10      0
         2                    8              0       8

预期输出：

1. ClassroomList[1].Studentlist[2]
2. ClassroomList[1].Studentlist[9]
3. ClassroomList[1].Studentlist == null

Answer 1

根据编辑后的预期输出，您可以使用：

 var results = (from r in ClassroomList
               let grp = r.StudentList.GroupBy(x => x.IsMale)
               select new
               {
                   ClassRoomsCount = ClassroomList.Count(),
                   StudentsCount = r.StudentList.Count,
                   Male = grp.Where(x => x.Key).Count(),
                   Female = grp.Where(x => !x.Key).Count()
               }).ToList();

旁注：你可以删除这一行public ClassroomList(){}编译器已经创建了一个隐藏的默认构造函数，所以你不需要自己做。

Answer 2

你们都在那里，只需使用 All 扩展名。

ClassroomList.Where(x => x.StudentList.All(y => y.IsMale));

更新问题后，您似乎需要这样的东西。

var result = ClassroomList
                .Select(x=> new 
                 {
                     StudentListCount = x.StudentList.Count(),
                     MaleCount = x.StudentList.Count(c=>c.IsMale),
                     FemaleCount = x.StudentList.Count(c=>!c.IsMale),
                 };

Answer 3

添加内部 where 过滤器。

ClassroomList.Where(x => x.StudentList.All(y => y.IsMale) );

更新：所以你需要这样吗？

ClassroomList.Select(x => new ClassroomList{ StudentList = x.StudentList.Where(y => y.IsMale).ToList() } );

如何在 LINQ 中包含基于条件的列表

How to include list based on a condition in LINQ

c#

linq

any