Filter lists with LINQ-CodePudding

I have, list Students and Teachers

var students = new List<Student>
    {
        new Student
        {
            Id= 1,
            Name = "AA",
            City = "London",
            Country = "UK"
        },
        new Student
        {
            Id= 2,
            Name = "BB",
            City = "New Orleans",
            Country = "USA"
        }
    }

var teachers = new List<Teacher>
    {
        new Teacher
        {
            Id = 1,
            Name = "CC",
            City = "Berlin",
            Country = "Germany"
        },
        new Teacher
        {
            Id = 2,
            Name = "DD",
            City = "Mexico D.F.",
            Country = "Mexico"
        }
    }

I wanted, for each teacher, get a list of students located in the same country and the same city.

What I did so far:

var result = from teacher in teachers
                     select new
                     {
                         teacher,
                         Students = students.Where(s => s.Country == teacher.Country && s.City == teacher.City).ToList()
                     };

This not worked, I got casting exception. And tried with:

var result = new List<(Teacher, IEnumerable<Student>)>();

teachers.ToList().ForEach(c => result.Add((c,
        students.Where(s => s.Country == c.Country && s.City == c.City).ToList())));

This worked fine but, is there any other ways, without looping?

CodePudding user response：

Your linq query is correct. Your query returns a list of anonymous type. You cannot cast it directly to a tuple list. The problem you have is which type you are trying to cast to. If you are trying to get a result of Tuple list like IEnumerable<(Teacher, IEnumerable)> you should code as below:

        var result = from teacher in teachers
                     select (
                         teacher,
                         students.Where(s => s.Country == teacher.Country && s.City == teacher.City).ToList()
                         );

Then, result.ToList() would give you a List of Tuple, result.ToArray() would give you an array of Tuple

Lambda expression alternative:

var result = teachers
            .Select(teacher => (teacher, students.Where(s => s.Country == teacher.Country && s.City == teacher.City).ToList()));

However, I would prefer anonymous list as a return type rather than Tuple.