通过另一个列表/数组筛选Linq子集合

using System;
using System.Collections.Generic;
using System.Linq;

public class Student
{
    public int Id { get; set; }
    public string Name { get; set; }
}

public class Grade
{
    public int StudentId { get; set; }
    public int Score { get; set; }
}

public class Program
{
    public static void Main()
    {
        List<Student> students = new List<Student>
        {
            new Student { Id = 1, Name = "Alice" },
            new Student { Id = 2, Name = "Bob" },
            new Student { Id = 3, Name = "Charlie" }
        };

        List<Grade> grades = new List<Grade>
        {
            new Grade { StudentId = 1, Score = 85 },
            new Grade { StudentId = 2, Score = 92 },
            new Grade { StudentId = 3, Score = 78 }
        };

        int threshold = 80;

        var highScoringStudents = students
            .Where(student => grades.Any(grade => grade.StudentId == student.Id && grade.Score > threshold))
            .ToList();

        foreach (var student in highScoringStudents)
        {
            Console.WriteLine(student.Name);
        }
    }
}

var highScoringStudents = from student in students
                          join grade in grades on student.Id equals grade.StudentId
                          where grade.Score > threshold
                          select student;

highScoringStudents = highScoringStudents.Distinct().ToList();

var gradeDict = grades.ToDictionary(g => g.StudentId, g => g.Score);

var highScoringStudents = students
    .Where(student => gradeDict.TryGetValue(student.Id, out int score) && score > threshold)
    .ToList();