static async Task ShowRegistrations_Good(IDac dac)
{
// Registrations
var regs = await dac.GetRegistrations(it => true);
// Students
var relatedStudentIdQry = regs.Select(it => it.StudentId).Distinct();
var students = await dac.GetStudents(it => relatedStudentIdQry.Contains(it.Id));
// Subjects
var relatedSubjectIdQry = regs.Select(it => it.SubjectId).Distinct();
var subjects = await dac.GetSubjects(it => relatedSubjectIdQry.Contains(it.Id));
// Teachers
var relatedTeacherIdQry = subjects.Select(it => it.TeacherId).Distinct();
var teachers = await dac.GetTeachers(it => relatedTeacherIdQry.Contains(it.Id));
foreach (var reg in regs)
{
var student = students.FirstOrDefault(it => it.Id == reg.StudentId);
var subject = subjects.FirstOrDefault(it => it.Id == reg.SubjectId);
var teacher = teachers.FirstOrDefault(it => it.Id == subject.TeacherId);
Console.WriteLine($"{reg.Id:00}|{subject.Name}, {student.Name}, {teacher.Name}, {reg.Semester}, {reg.Grade}");
}
}
static async Task ShowRegistrationsWithCondition_Good(IDac dac)
{
var regs = await dac.GetRegistrations(it => true);
var evenRegs = regs.Where(it => it.Id % 2 == 0);
Console.WriteLine($"Any event Id in the registrations? {evenRegs.Any()}");
}
static async Task FilterRegistrations_Bad(IDac dac)
{
var firstSemesters = await dac.GetRegistrations(it => it.Semester == "1st" && it.Grade == 0);
var secondSemester = await dac.GetRegistrations(it => it.Semester == "2nd" && it.Grade == 0);
Console.WriteLine("Fail students in the 1st semester");
foreach (var item in firstSemesters)
{
var student = await dac.GetStudent(it => it.Id == item.StudentId);
Console.WriteLine(student.Name);
}
Console.WriteLine("Fail students in the 2nd semester");
foreach (var item in secondSemester)
{
var student = await dac.GetStudent(it => it.Id == item.StudentId);
Console.WriteLine(student.Name);
}
}
static async Task ShowRegistrations_Bad(IDac dac)
{
var regs = await dac.GetRegistrations(it => true);
foreach (var reg in regs)
{
var student = await dac.GetStudent(it => it.Id == reg.StudentId);
var subject = await dac.GetSubject(it => it.Id == reg.SubjectId);
var teacher = await dac.GetTeacher(it => it.Id == subject.TeacherId);
Console.WriteLine($"{reg.Id:00}|{subject.Name}, {student.Name}, {teacher.Name}, {reg.Semester}, {reg.Grade}");
}
}
static async Task ShowRegistrationsWithCondition_Bad(IDac dac)
{
var regs = await dac.GetRegistrations(it => true);
var evenRegs = new List <Registration>();
foreach (var item in regs)
{
if (item.Id % 2 == 0)
{
evenRegs.Add(item);
}
}
Console.WriteLine($"Any event Id in the registrations? {evenRegs.Count() > 0}");
}
static async Task FilterRegistrations_Good(IDac dac)
{
var fails = await dac.GetRegistrations(it => it.Grade == 0);
var firstSemesters = fails.Where(it => it.Semester == "1st");
var secondSemester = fails.Where(it => it.Semester == "2nd");
var studentIdQry = fails.Select(it => it.StudentId).Distinct();
var students = await dac.GetStudents(it => studentIdQry.Contains(it.Id));
Console.WriteLine("Fail students in the 1st semester");
foreach (var item in firstSemesters)
{
var student = students.FirstOrDefault(it => it.Id == item.StudentId);
Console.WriteLine(student.Name);
}
Console.WriteLine("Fail students in the 2nd semester");
foreach (var item in secondSemester)
{
var student = students.FirstOrDefault(it => it.Id == item.StudentId);
Console.WriteLine(student.Name);
}
}