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在我的应用程序中,我试图编写一个ListStudents ActionResult,它只显示一个列表,其中的ClassroomID等于当前登录的教师创建的ClassroomID之一。ASP.NET MVC 4,EF和LINQ:为多对多关系创建特定的LINQ查询
我相信我需要使用一些LINQ查询来获得所需的结果,但是我被卡住了,因为当教师实体拥有教室ICollection时,我不知道如何处理它。
ListStudents & CreateClassroom我TeacherController
public ActionResult ListStudents()
{
//This gets the current teachers UserProfile as only users with the teacher role have access to this controller
var teacherProfile = db.UserProfiles.Local.SingleOrDefault(u => u.UserName == User.Identity.Name)
?? db.UserProfiles.SingleOrDefault(u => u.UserName == User.Identity.Name);
var teacher = db.Teachers.Find(teacherProfile.UserId);
//Need query where students ClassroomID needs to be one of the current teachers ClassroomID's
return View(students);
}
public ActionResult CreateClassroom(Classroom model)
{
if (ModelState.IsValid)
{
try
{
var userProfile = db.UserProfiles.Local.SingleOrDefault(u => u.UserName == User.Identity.Name)
?? db.UserProfiles.SingleOrDefault(u => u.UserName == User.Identity.Name);
var classroom = new Classroom
{
ClassroomName = model.ClassroomName,
TeacherID = userProfile.UserId
};
db.Classrooms.Add(classroom);
db.SaveChanges();
}
catch (DataException)
{
ModelState.AddModelError("", "Something went wrong, try again.");
}
}
return RedirectToAction("ListClassrooms");
}
模式对于用户,学生,教师和课堂
public class User
{
[Key]
[Editable(false)]
[ForeignKey("UserProfile")]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.None)]
public int UserId { get; set; }
public virtual UserProfile UserProfile { get; set; }
[Display(Name = "First Name")]
[Required(ErrorMessage = "First name is required.")]
[MaxLength(50)]
public virtual string FirstName { get; set; }
[Display(Name = "Last Name")]
[Required(ErrorMessage = "Last name is required.")]
[MaxLength(50)]
public virtual string LastName { get; set; }
}
学生
public class Student : User
{
[ForeignKey("Account")]
[Editable(false)]
public virtual int AccountID { get; set; }
public virtual Account Account { get; set; }
[Column("ClassroomID")]
[ForeignKey("Classroom")]
public virtual int ClassroomID { get; set; }
public virtual Classroom Classroom { get; set; }
}
教师
public class Teacher : User
{
public virtual ICollection<Classroom> Classrooms { get; set; }
}
课堂
public class Classroom
{
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public virtual int ClassroomID { get; set; }
[Display(Name = "Classroom Name")]
[MaxLength(50)]
public virtual string ClassroomName { get; set; }
public virtual ICollection<Student> Students { get; set; }
[Column("TeacherID")]
[ForeignKey("Teacher")]
public virtual int TeacherID { get; set; }
public virtual Teacher Teacher { get; set; }
}
感谢您抽出时间来帮我解决这个问题,我是很新的MVC和我试图尽可能多的学习,因为我能够。
非常感谢你,完美的工作!我在理解第一个查询正在做什么时遇到了一些麻烦。如果你不介意的话,你能否告诉我它正在做什么? –
您需要查询的第一件事是教室的集合。一旦你有了这些教室,你就可以看到学生属于那些教室。在第一个查询中,我使用WHERE子句获得了一批教室。从那个集合中,我只关心Ids(这是SELECT子句的作用)。教室变量实际上只是一个整数集合。 – mtm927
非常感谢! –