[C# interview] students and courses

// Найдите любые ошибки/улучшения в следующем фрагменте кода
using System.Collections.Generic;
using System.Linq;

public static class Enumerable
{
    public class StudentAndCourse
    {
        public Student Student { get; set; }
        public Course Course { get; set; }
    }

    public class Student
    {
        public string Name { get; set; }
        public int? Course { get; set; }
    }

    public class Course
    {
        public int? CourseID { get; set; }
        public string Namе { get; set; }
    }

    public static IEnumerable<StudentAndCourse> Do(IEnumerable<Student> students, IEnumerable<Course> courses)
    {
        if (students.Count() == 0)
            return new List<StudentAndCourse>();
        var result = new List<StudentAndCourse>();
        foreach (var student in students)
        {
            result.Add(new StudentAndCourse()
            {
                Student = student,
                Course = courses.Single(d => d.CourseID == student.Course)
            });
        }

        return result;
    }
}