public IEnumerable <Student> GetStudents()
{
var db = new s5554Context();
var students = db.Student.ToList();
return(students);
}
public static void InsertExamples()
{
var db = new s5554Context();
var s = new Student
{
FirstName = "Kamil",
LastName = "Potocki"
};
db.Student.Add(s);
db.SaveChanges();
}
public Student UpdateStudent(string id, string lastname)
{
var db = new s5554Context();
// update
var st1 = db.Student.Find(id);
st1.LastName = lastname;
db.SaveChanges();
return(st1);
}
public Student RemoveStudent(string id)
{
var db = new s5554Context();
var s = new Student
{
IndexNumber = id
};
db.Attach(s);
db.Remove(s);
db.SaveChanges();
return(s);
}
public static void RemoveExamples()
{
var db = new s5554Context();
// usuwanie studenta pobierajac go najpierw
/* var st = db.Student.OrderByDescending(s => s.IndexNumber).First();
* db.Student.Remove(st);*/
var s = new Student
{
IndexNumber = "111"
};
db.Attach(s); // dolaczanie obiektu
db.Remove(s); // ustawienie flagi na Deleted i usiniecie
//db.Entry(s).State = EntityState.Deleted; to samo co dwie komendy powyzej
db.SaveChanges();
}
public static void QueryExamples()
{
var db = new s5554Context();
// SELECT * FROM Student
//var students = db.Student.ToList();
// wszyscy studenci ktorych imie zaczyna sie na
/* var student = db.Student
* .Where(s => s.FirstName.StartsWith("K"))
* .OrderBy(s => s.LastName)
* .ThenBy(s => s.FirstName)
* .ToList();*/
// Lazy Loading
/* var student = db.Student
* .Where(s => s.FirstName.StartsWith("K"))
* .OrderBy(s => s.LastName)
* .ThenBy(s => s.FirstName);*/
/* var students = db.Student.ToList();
*
* int g = 0;
* // problem N+1
* foreach(var s in students) // tu jest SELECT * FROM Student
* {
*
* }*/
//var student = db.Student.OrderBy(s => s.LastName);
//var student2 = student.Where(s => s.LastName == "Potocki");
/*var students = db.Student
* .GroupBy(s => s.FirstName)
* .Select(s => new
* {
* Imie = s.Key,
* LiczbaStudentow = s.Count()
* }).ToList();*/
}
public static void UpdateExamples()
{
var db = new s5554Context();
// update
/*var st1 = db.Student.First(); // pierwszy rekord z bazy
* st1.LastName = "Zmiana";*/
//db.SaveChanges(); // wysylanie zmian z kolekcji sa wysylane w jednej transakcji do bazy
//db.SaveChangesAsync();
// update studenta ktorego jeszcze nie ma, zostanie on stworzony
var st1 = new Student
{
IndexNumber = "8",
LastName = "Drewniany"
};
db.Attach(st1);
//db.Entry(st1).Property("LastName").IsModified = true;
db.SaveChanges();
}
