I'm struggling to get relationships working with EF6 and data annotations.
I have three (3) tables: Theme, ThemeType, ThemeSection
A theme can contain a type and a section, so I've constructed my table as such:
Theme
Id: int, autoincrement
TypeId: int
SectionId: int
then,
ThemeType
Id: int, autoincrement
and,
ThemeSection
Id: int, autoincrement
For my code-first class updates, I did the following:
[Table("theme")]
public class Theme: IDomain
{
[Autoincrement, Column("id"), Key]
public int Id { get; set; }
[Column("type_id")]
public int TypeId { get; set; }
[Column("section_id")]
public int SectionId { get; set; }
[ForeignKey("TypeId")]
public virtual ThemeType Type { get; set; }
[ForeignKey("SectionId")]
public virtual ThemeSection Section { get; set; }
}
and
[Table("theme_type")]
public class ThemeType: IDomain
{
[Autoincrement, Column("id"), Key]
public int Id { get; set; }
[ForeignKey("Id")]
public virtual Theme Theme { get; set; }
}
and finally:
[Table("theme_section")]
public class ThemeSection: IDomain
{
[Autoincrement, Column("id"), Key]
public int Id { get; set; }
[ForeignKey("Id")]
public virtual Theme Theme { get; set; }
}
Based on this link here, you need to define the ForeignKey(s) in the top-level, which is Theme, and I've done so based on the commented out code, but it does not work. Keep getting an error about multiplicity?
I followed the example from Learn Entity Framework, and got it working to an extent, still don't know what I did wrong.
Related
I am using EF 6.1.1.
I am unable to figure out how to create One-to-One relationship between two classes/tables with both entities have their owns PKs. I originally posted question link but could not get much help on it OR i am not able to get it. So, here i am putting my question in simple way.
Appreciate if someone can share thoughts on it.
My Requirement:
I would like create One-To-One relationship between Principle and Dependant with 'Id' from Principle class acts as Foreign Key in dependant class.
Principle Class
public class Student
{
public string FullName {get; set;}
}
Dependant Class
public class StudentReport
{
public string RollNumber { get; set; }
public string StudentType { get; set; }
}
Add PKs – EF requires this:
public class Student
{
public int Id { get; set; }
public string FullName { get; set; }
}
public class StudentReport
{
public int Id { get; set; }
public string RollNumber { get; set; }
public string StudentType { get; set; }
}
Note that EF 5 and later supports naming conventions: Id indicates a primary key. Alternately, it also supports the name of the class followed by "Id", so the above keys could have been StudentId for Student and StudentReportId for StudentReport, if you wished.
Add the foreign relation as a navigation property to at least one of the tables – in this case, you stated that StudentReport is the dependent, so let's add it to that one:
public class Student
{
public int Id { get; set; }
public string FullName { get; set; }
}
public class StudentReport
{
public int Id { get; set; }
public string RollNumber { get; set; }
public string StudentType { get; set; }
public Student Student { get; set; }
}
Again – by naming convention – EF determines that a single Student property on StudentReport indicates that this is a navigational property associated with a foreign key. (By defining only the Student property, but no foreign key property, you are indicating that you don't care what EF names the associated FK ... basically, you're indicating you'll always access the related Student via the property.)
If you did care about the name of the FK property, you could add it:
public class Student
{
public int Id { get; set; }
public string FullName { get; set; }
}
public class StudentReport
{
public int Id { get; set; }
public string RollNumber { get; set; }
public string StudentType { get; set; }
public int StudentId { get; set; }
public Student Student { get; set; }
}
Again – by naming convention – EF determines that StudentId is the FK associated with the Student property because it has the class name, "Student", followed by "Id".
All of this, so far, has been using conventions as defined in Entity Framework Code First Conventions, but Data Annotations are also an option, if you wish:
public class Student
{
[Key]
public int Id { get; set; }
public string FullName { get; set; }
}
public class StudentReport
{
[Key]
public int Id { get; set; }
public string RollNumber { get; set; }
public string StudentType { get; set; }
[ForeignKey("Student")]
public int StudentId { get; set; }
public Student Student { get; set; }
}
Doing this is actually a good idea, because it makes clearer your intent to other programmers that might not be aware of EF Conventions – but can easily infer them from simply looking at EF Data Annotations – and is still less cumbersome than Fluent API.
UPDATE
I just realized, I left this as a one-to-many, with enforcement of the one-to-one relationship being left to do in the code using this model. To enforce the one-to-one in the model, you could add a navigation property to the Student class going the other way:
public class Student
{
public int Id { get; set; }
public string FullName { get; set; }
public StudentReport StudentReport { get; set; }
}
public class StudentReport
{
public int Id { get; set; }
public string RollNumber { get; set; }
public string StudentType { get; set; }
public Student Student { get; set; }
}
However, that's going to break, because EF doesn't know which entity to insert first on an add. To indicate which is dependent, you have to specific that the dependent class' PK is the FK to the principal class (this enforces one-to-one because – in order for a Student/StudentReport pair to be associated – their Id properties must be the exact same value):
public class Student
{
public int Id { get; set; }
public string FullName { get; set; }
public StudentReport StudentReport { get; set; }
}
public class StudentReport
{
[ForeignKey("Student")]
public int Id { get; set; }
public string RollNumber { get; set; }
public string StudentType { get; set; }
public Student Student { get; set; }
}
or, using the full set of Data Annotations from earlier:
public class Student
{
[Key]
public int Id { get; set; }
public string FullName { get; set; }
public StudentReport StudentReport { get; set; }
}
public class StudentReport
{
[Key, ForeignKey("Student")]
public int Id { get; set; }
public string RollNumber { get; set; }
public string StudentType { get; set; }
public Student Student { get; set; }
}
I've the following situation I try to solve : I've 2 tables, a Course table with some fields and a CourseDescription table which is optional (so Course may have a CourseDescription but CourseDescription must have a Course). I'm trying to set this up. So far, here's what I have :
public class Course
{
[Key, Column("Key_Course")]
public int ID { get; set; }
public string Name { get; set; }
public virtual CourseDescription CourseDescription { get; set; }
}
public class CourseDescription
{
[Key, ForeignKey("Course")]
public int ID { get; set; }
public string Description { get; set; }
public string PreRequis { get; set; }
public int CoursesID { get; set; }
[ForeignKey("CoursesID")]
public Course Course { get; set; }
}
This "works" meaning that EF doesn't complains about my model but the relation is not properly done because EF associate the PK of CourseDescription with the PK of Course. In my database, this is not the case (ex : CourseDescription.ID=1 is associated with CourseDescription.CoursesID=3, not 1).
Is there a way to fix that with data annotation ? I know I can use the fluent API but I don't want to override the model building just for that (unless there's no other way).
Thanks
Well, I think you have two choices:
Configure an one to many relationship
If you want to map the FK of the relationship between Course and CourseDescription, and you don't want to declare that FK property as Key of the CourseDescription entity, then, you don't have other choice that configure an one-to-many relationship. In that case your model would be like this:
public class Course
{
[Key, Column("Key_Course")]
public int ID { get; set; }
public string Name { get; set; }
public virtual ICollection<CourseDescription> CourseDescriptions { get; set;}
}
public class CourseDescription
{
[Key]
public int ID { get; set; }
public string Description { get; set; }
public string PreRequis { get; set; }
[ForeignKey("Course")]
public int CourseID { get; set; }
public Course Course { get; set; }
}
Configure an one-to-one relationship but not map the FK of the
relationship
The only way that EF lets you map the FK in an one-to-one relationship is when the FK is declared as a PK too, so if you want to have diferent Ids in both entities and you want to stablish an one-to-one relationship, then you could do something like this:
public class Course
{
[Key, Column("Key_Course")]
public int ID { get; set; }
public string Name { get; set; }
public CourseDescription CourseDescription { get; set;}
}
public class CourseDescription
{
[Key]
public int ID { get; set; }
public string Description { get; set; }
public string PreRequis { get; set; }
[Required]
public Course Course { get; set; }
}
And work with the navigations properties.
It looks like you should not use ForeignKey attribute for ID property of CourseDescription class as you don't want to have an association between primary keys. Try to remove it.
Edit: It looks like I misunderstood the question previous time.
You can have your CourseDescription this way.
public class CourseDescription
{
[Key, ForeignKey("Course")]
public int ID { get; set; }
public string Description { get; set; }
public string PreRequis { get; set; }
public Course Course { get; set; }
}
In this case you don't need to have CoursesID field. Entities will be connected by primary keys.
I have two database tables:
Customers
CustomerId (PK)
Name
...
CustomerSettings
CustomerId (PK)
Setting1
Setting2
...
Is it possible to have these classes using code-first? If so, what is the fluent mapping?
public class Customer
{
public int CustomerId { get; set; }
public int Name { get; set; }
public CustomerSetting CustomerSetting { get; set; }
}
public class CustomerSetting
{
public int CustomerId { get; set; }
public int Setting1 { get; set; }
public int Setting2 { get; set; }
public Customer Customer { get; set; }
}
I personally don't like one-to-one tables. After all, why not just add the setting columns to the customer table? Unfortunately, this is what I need to develop against. I can't figure the correct code-first mappings for such a scenario. Thanks for your help.
If you are going for code first and want to have both Customer And CustomerSettings classes,
but only a single table for both, as your post suggests ,
I would use complex types.
see a good example here:
http://weblogs.asp.net/manavi/archive/2010/12/11/entity-association-mapping-with-code-first-part-1-one-to-one-associations.aspx
So , your object model should look like this (I've not tested it):
public class Customer
{
public Customer()
{
CustomerSetting= new CustomerSetting();
}
public int CustomerId { get; set; }
public int Name { get; set; }
public CustomerSetting CustomerSetting { get; set; }
}
[ComplexType]
public class CustomerSetting
{
public int CustomerId { get; set; }
public int Setting1 { get; set; }
public int Setting2 { get; set; }
public Customer Customer { get; set; }
}
Your model classess are correct, if you want you can add this to your model builder to specify which table is the "main one":
.Entity<Customer>()
.HasOptional(c => c.CustomerSetting)
.WithRequired(u => u.Customer);
For all classes in my Entity I have a base class named CommonFields
public class CommonFields
{
public int Status { get; set; }
public DateTime CreatedOn { get; set; }
public int CreaedBy { get; set; }
public DateTime ModifiedOn { get; set; }
public int ModifiedBy { get; set; }
}
And, for eg. I have two classes like
public class Employee : CommonFields
{
public int Id { get; set; }
public string Name { get; set; }
//Other properties
}
public class User : CommonFields
{
public int Id { get; set; }
public string Name { get; set; }
//Other properties
}
How can I set relation from CreatedBy & ModifiedBy to User table. I just need only one directional mapping (I don't want FK to be created in my User Table).
I need to get User information when I write objEmployee.CreatedUser
Thanks.
I have a code first class
public class test
{
public int ID { get; set; }
public int ManagerID { get; set; }
[ForeignKey("ManagerID")]
public Person Manager { get; set; }
}
In databas table is created correctly, however then I try to access
pTest.Manager it returns null
In database table test field ManagerID has correct id value for person.
Make the Manager property virtual so that EF can lazy load it or use eager loading(using the Include method).
public class test
{
public int ID { get; set; }
public int ManagerID { get; set; }
[ForeignKey("ManagerID")]
public virtual Person Manager { get; set; }
}