public static void ejemplos()
{
//EJEMPLOS QUERIES
using (var dbcontext = new SchoolDBEntities())
{
//EJEMPLO SQL QUERY:
var studentEntity = dbcontext.Students.SqlQuery("select * from student").ToList <Student>();
//EJEMPLO LIKE
var Teacher = (from t in dbcontext.Teachers
join c in dbcontext.Courses on t.TeacherId equals c.TeacherId
where c.CourseName.Contains("Science")
select new TeacherEntities
{
teacherName = t.TeacherName,
courseName = c.CourseName
}).ToList();
}
//EJEMPLO Eager Loading
//Trae las entidades relacionadas, en este caso Standard y Teachers
using (var context = new SchoolDBEntities())
{
var stud1 = (from s in context.Students.Include("Standard.Teachers")
select s).ToList <Student>();
}
//EJEMPLO LAZY Loading es lo contrario al eager loading, trae la propiedad especificada
//de forma independiente
using (var ctx = new SchoolDBEntities())
{
//Loading students only
IList <Student> studList = ctx.Students.ToList <Student>();
Student std = studList[0];
//Loads Student address for particular Student only (seperate SQL query)
StudentAddress add = std.StudentAddress;
}
//EJEMPLO Explicit Loading
//Trae entitdades relacionadas de forma explicita
using (var context = new SchoolDBEntities())
{
var student = context.Students
.Where(s => s.StudentName == "Student5")
.FirstOrDefault <Student>();
context.Entry(student).Reference(s => s.StudentAddress).Load(); // loads StudentAddress
context.Entry(student).Collection(s => s.Courses).Load(); // loads Courses collection
}
//EJEMPLO UPDATE
//using (var context = new SchoolDBEntities())
//{
// var std = (from s in context.Students where s.StudentID==5 select s).FirstOrDefault<Student>();
// std.StandardId = 1;
// context.SaveChanges();
//}
//EJEMPLO INSERT
//using (var context = new SchoolDBEntities())
//{
// var std = new Student()
// {
// StudentName = "Walitas"
// };
// context.Students.Add(std);
// context.SaveChanges();
//}
//EJEMPLO DELETE
//using (var context = new SchoolDBEntities())
//{
// var std = context.Students.First<Student>();
// context.Students.Remove(std);
// context.SaveChanges();
//}
}
