如何编写处理与用C＃中的外键连接的表的Web API？

Question

I am trying to write a web api for a student table and the lessons that the student takes. The controllers are working fine individually. I mean get, post, put and delete methods are working.

Student Table has an id as primary key, a name and courses

Courses Table has an id as primary key, student id as foreign key and the name of the course

The model classes are

    public class Student
    {
        public int id { get; set; }
        public string name{ get; set; }
        public ICollection<Courses> Courses { get; set; } 
    }

    public class Courses
    {
        public int id { get; set; }
        public int studentid { get; set; }
        public string name{ get; set; }
    }

The project on which I am working is a .net web api project. The post method I have written for the student is as below

        try
        {
            using (var connection = new SqlConnection(connectionString))
            {
                connection.Open();

                using (var cmd = new SqlCommand())
                {
                    cmd.CommandType = System.Data.CommandType.Text;
                    cmd.CommandText = "insert into student (name) " +
                        "values (@name)";

                    cmd.Connection = connection;
                    cmd.Parameters.AddWithValue("@name", student.name);

                    cmd.ExecuteNonQuery();
                }
            }
        }
        catch (SqlException ex)
        {

            Debug.WriteLine(ex.Message);
        }

Here is my question. How do I write my methods with taking the foreign key into account? I could not find any code examples. All of them are for entity framework...

Answer 1

For example to get all students and courses you can use:

[HttpGet]
public ActionResult<StudentViewModel> GetAllStudents()
{
        try
        {
            using (var connection = new SqlConnection(connectionString))
            {
                connection.Open();

                using (var cmd = new SqlCommand())
                {
                    cmd.CommandType = System.Data.CommandType.Text;
                    cmd.CommandText = "SELECT s.id, s.name, c.Name as courseName FROM Student s INNER JOIN Courses c on c.studentId = s.id";
                    cmd.Connection = connection;


                    SqlDataAdapter da = new SqlDataAdapter(cmd);

                    da.Fill(dataTable);
                    connection.Close();
                    da.Dispose();

                    //Fill result view model from dataTable which will contain all data which you want from DB. 
                }
            }
        }
        catch (SqlException ex)
        {
            //Log exception
        }
}

But this is only sample. In real world much better to split logic between action in the controller and business logic for getting data. And to use object-relational mapping (ORM) like EntityFramework will save a lot of time. And if you need to use custom query you will have possibility to do it.