如何使用 MySQL 数据填充包含每个类项的类列表的类列表？

Question

This is one of the classes I have in C# :

public class Courses
    {
        [DataMember]
        public string SchoolName { get; set; }
        [DataMember]
        public string MajorName { get; set; }
        [DataMember]
        public List<string> Course { get; set; }

        public Courses()
        {
            Course = new List<string>();
        }
    }

For each Major, there is a list of classes.

In my database, I have three tables for school, major and courses joined with foreign leys. A simple SQL table to read them would be for a given school :

SELECT 
major.MajorName,
course.CourseName 
FROM school
INNER JOIN major ON major.MajorID = course.MajorID  
WHERE school.SchoolName = @SchoolName AND major.SchoolNameID = school.SchoolNameID GROUP BY major.MajorName;

So based on this, I expect the data as follows. (Multiple major names and each major with multiple courses)

MajorName   CourseName
Science      SC101
Science      SC102
Science      SC500
Math         MA100
Math         MA200
ENGLISH      EN450

What is the best way I could populate the class I derived at the beginning? My class definision inside database read query would be :

List<Courses> majorclasses = new List<Courses>() 

I could manual manage the data to populate the class by reading distinct majorNames and then populating each course for each majorName in a loop.

(pheudo code)
List<string> distinctMajors = majorClasses.Disticnt("majorNames").ToList()
foreach major in distinctMajors
{
   course.Add(courseName)
}

Any other better method to acheive this ?

Answer 1

You can try this.

List<Courses> courses =  data.GroupBy(
    d => new { d.SchoolName, d.MajorName},
    d => d.CourseName,
    (key,g) => new Courses {
        MajorName = key.MajorName,
        SchoolName = key.SchoolName,
        Course = g.Distinct().ToList() }
    ).ToList();