如何使用 linq 将列表中的列表转换为单个列表 [重复]

Question

如果我有如下对象：

public class Teacher
{
    public int TeacherId { get; set; }
    public string TeacherName { get; set; }
    public List<string> StudentNames { get; set; }
}

我想将其翻译成一个列表，其中每个教师姓名与每个学生姓名配对。

public class TeacherStudent
{

    public int TeacherId { get; set; }
    public string TeacherName { get; set; }
    public string StudentName { get; set; }

}

我知道我可以通过这样的循环来做到这一点：

var teachers = new List<Teacher>();
teachers.Add(new Teacher() { TeacherId = 1, TeacherName = "Teacher1", StudentNames = new List<string>() { "Student1", "Student2" } });
teachers.Add(new Teacher() { TeacherId = 2, TeacherName = "Teacher2", StudentNames = new List<string>() { "Student3", "Student4", "Student5" } });
teachers.Add(new Teacher() { TeacherId = 3, TeacherName = "Teacher3", StudentNames = new List<string>() { "Student6", "Student7" } });


var teacherStudents = new List<TeacherStudent>();
foreach(var teacher in teachers)
{

    foreach (var studentName in teacher.StudentNames)
    {
        teacherStudents.Add(new TeacherStudent() { TeacherId = teacher.TeacherId, TeacherName = teacher.TeacherName, StudentName = studentName });
    }

}

似乎应该有一种方法可以用 linq 做到这一点，但我无法弄清楚。

Answer 1

你可以使用SelectMany:

teachers.SelectMany(t =>
            t.StudentNames.Select(s => new TeacherStudent
            {
                TeacherId = t.TeacherId,
                TeacherName = t.TeacherName,
                StudentName = s
            }));