无法隐式转换类型错误

Question

我有一个任务是创建一个类Student并创建一个方法,只有当他们的名字在使用LINQ查询运算符的字母顺序排在他们的姓氏之前时才从数组中选择Students.我写过这Student堂课:

public class Student
{
     private string firstName;
     private string familyName;
     private int age;

    public Student(string firstName, string familyName, int age)
        : this()
    {
        this.firstName = firstName;
        this.familyName = familyName;
        this.age = age;
    }

    public Student()
    {
        firstName = "Dancho";
        familyName = "Mastikata";
        age = 24;
        this.firstName = firstName;
        this.familyName = familyName;
        this.age = age;
    }

    public string FirstName
    {
        get { return firstName; }
        set { firstName = value; }
    }

    public string FamilyName
    {
        get { return familyName; }
        set { familyName = value; }
    }

    public int Age
    {
        get { return age; }
        set { age = value; }
    }
}

然后我编码了这个:

public class StudentsManipulations
{
    static void Main()
    {
        Student[] students = new Student[6]{new Student("Georgi", "Milanov", 21      ),
                                            new Student("Ilko", "Pirgov", 30         ),
                                            new Student("Neboisha", "Yelenkovich", 34),
                                            new Student("Dimitar", "Berbatov", 32    ),
                                            new Student(                             ),
                                            new Student("Nikolai", "Bodurov", 24     )};

    }

    public static List<Student> StudentSortByFirstName(Student[] students)
    {
        List<Student> sortedStudents = from student in students 
             where student.FirstName.CompareTo(student.FamilyName) < 0 
             select student;

        return sortedStudents;
    } 
}            

不幸的是,关键字在哪里出错,我无法完全理解:

无法将类型'System.Collections.Generic.IEnumerable'隐式转换为'System.Collections.Generic.List'.存在显式转换(您是否错过了演员？).

你能帮我理解究竟是什么问题吗？

Answer 1

使用ToList()方法枚举结果并将它们放入列表中:

var query = from student in students
            where student.FirstName.CompareTo(student.FamilyName) < 0
            select student;

List<Student> sortedStudents = query.ToList();

或者在一个声明中:

List<Student> sortedStudents = (from student in students
                                where student.FirstName.CompareTo(student.FamilyName) < 0
                                select student).ToList();