Scenario seems to be trivial and I'm really confused on what I'm doing wrong.
So, I have a Client class
public class Client
{
[Key]
public int ClientID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public virtual Account Account { get; set; }
}
Employee class
public class Employee
{
[Key]
public int EmployeeID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public virtual Account Account { get; set; }
}
and an Account class
public class Account
{
[Key]
public int AccountID { get; set; }
public string Login { get; set; }
public string Password { get; set; }
public virtual Employee Employee { get; set; }
public virtual Client Client { get; set; }
}
Both Client and Employee may have an Account or not ( online access is optional ). As database is not compatible with EF namingconvention I have to come up with Fluent API explicit mappings.
Both Client and Employee tables have "AccountID" column that I'm trying to use to build a relation.
modelBuilder.Entity<Client>()
.HasOptional(e => e.Account)
.WithRequired(a => a.Client)
.Map(m => m.MapKey("AccountID"));
modelBuilder.Entity<Employee>()
.HasOptional(e => e.Account)
.WithRequired(a => a.Employee)
.Map(m => m.MapKey("AccountID"));
but I get
Schema specified is not valid. Errors:
(15,6) : error 0019: Each property name in a type must be unique. Property name 'AccountID' was already defined.
(16,6) : error 0019: Each property name in a type must be unique. Property name 'AccountID' was already defined.
so, is there a way to fix this other than modification of the table/entity structure?
Turns out you don't need Fluent API in this case, what you need is to DataAnnotate your properties in Entities with InverseProperty attribute
[InverseProperty("AccountID")]
There is a great answer by Ladislav Mrnka in Entity Framework 4.1 InverseProperty Attribute question
However if anyone knows how to do that correctly with Fluent answers are highly appreciated
Related
I have Two Model
public class User: Entity
{
public string Gender { get; set; }
public string Name { get; set; }
}
And
public class CognitoUser : Entity
{
public string UserId { get; set; }
public User User{ get; set; }
public string CognitoName { get; set; }
}
I want to set Cognito.UserId as User.Id . I have written the following which is not working can you please correct me as i dont want to create a model CognitoUser into user model.
modelBuilder.Entity<CognitoUser>(e =>
{
e.ToTable("CognitoUser");
e.HasKey(p => p.UserId);
e.HasOne(x => x.User)
.HasForeignKey<User>(c => c.Id);
});
Primary keys are required in each Entity which is missing in your User Entity.
Using Fluent API is optional. If you set your classes right, Entity Framework will understand what you want to achieve.
Hints:
Use [Key] attribute to specify a property as primary key
Prefered primary key format would be {ClassName}{Id}
Use [DatabaseGenerated(DatabaseGeneratedOption.Identity)] to force database
to automatically generate primary key for you.
You can use Guid as primary key type, it is always unique and hassle-free
Additionally, check out the code below to see how to create a relation.
public class User: Entity
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public Guid UserId { get; set; }
public string Gender { get; set; }
public string Name { get; set; }
}
public class CognitoUser: Entity
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public Guid CognitoUserId { get; set; }
public string CognitoName { get; set; }
// relation
public Guid UserId { get; set; }
public User User { get; set; }
}
Visualization:
I have a many-to-many relationship between User(Contributor) and TaskType. I want to assign to a variable only TaskTypes that have the current user among their contributors. Obviously, I can somehow do this using the functionality of the Entity Framework. But how? I use asp.net core 3.
Below I try unsuccessfully to do it:
public IQueryable<TaskType> ContributedTaskTypes
{
get
{
// This code doesn't work!
return _dbContext.TaskTypes.Where(t => t.Contributors.Contains(c => c.UserId == CurrentUserId));
}
}
Below are definitions of all models involved in this relationship:
public class TaskType
{
public int Id { get; set; }
public string UserId { get; set; }
public ApplicationUser ApplicationUser { get; set; }
public virtual List<Contribution> Contributors { get; set; }
}
public class Contribution
{
public int Id { get; set; }
public string UserId { get; set; }
public ApplicationUser ApplicationUser { get; set; }
public int TaskTypeId { get; set; }
public TaskType TaskType { get; set; }
}
public class ApplicationUser : IdentityUser
{
public virtual List<Contribution> ContributedToTaskTypes { get; set; }
}
For those queries it is always easiest to do queries where you can dot to the result.
Here is the query with sql-like syntax
from row in _dbContext.Contribution
where row.UserId == CurrentUserId
select row.TaskType
By selecting row.TaskType instead of just row you get it correct entity.
Is that Contributors property retrieved correctly from DB? if it is not you must call Include() method to load/refer relational referenced entities
_dbContext.TaskTypes.Include(p=>p.Contributors).Where(..
more: https://learn.microsoft.com/en-us/ef/core/querying/related-data
In Addition, if EF Core Table Relation is not correctly defined, you should follow
this instruction: https://www.entityframeworktutorial.net/efcore/configure-many-to-many-relationship-in-ef-core.aspx
I'm trying to make one to one relationship. I don't want to use fluent API if it is not necessary. This is what I tried so far:
[Table("UserProfile")]
public class UserProfile
{
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public int UserId { get; set; }
public string UserName { get; set; }
}
public class Person
{
public int Id { get; set; }
[ForeignKey("UserId")]
public UserProfile UserProfile { get; set; }
}
Yes, I know there are few similar questions outhere, but none of them were short and clear. Lot of them also did not work.
It depends a little on what type of table structure you want to achieve. There are various ways of doing this, and there is a good walkthrough for all the options, from Shared Primary Key Assocations to One-to-One Foreign Key Associations in those links. Unfortunately those links make more use of Fluent than Annotations. The samples below use Annotations, as you need.
Shared Primary Key
In theory the Shared Primary Key (horizontal table partitioning, in database terms) is the "correct way". It is also the smallest change you need to do to be able to generate a migration (which will use a Shared Primary Key Association). Note that I would change Person.Id to Person.UserId to better show your intent:
// tested in EF 5 and MVC 4.5.
[Table("UserProfile")]
public class UserProfile {
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public int UserId { get; set; }
public string UserName { get; set; }
}
[Table("Person")] // not required, added for clarity in sample code
public class Person {
// Note the change of property name to reflect that this is a shared primary key,
// using the UserId column in UserProfile as the Primary Key
[Key]
public int UserId { get; set; }
[ForeignKey("UserId")]
public virtual UserProfile UserProfile { get; set; }
}
// The generated migration:
public partial class AddTable_Person : DbMigration
{
public override void Up() {
CreateTable(
"dbo.Person",
c => new {
UserId = c.Int(nullable: false),
})
.PrimaryKey(t => t.UserId)
.ForeignKey("dbo.UserProfile", t => t.UserId)
.Index(t => t.UserId);
}
public override void Down(){
DropIndex("dbo.Person", new[] { "UserId" });
DropForeignKey("dbo.Person", "UserId", "dbo.UserProfile");
DropTable("dbo.Person");
}
}
this then gives you, in effect a 1:0-1 relationship between UserProfile (which is mandatory) and People (which is optional, but can have one per person at the most.
If you want to use Id in Person then do the following (the migration will change accordingly):
public class Person {
public int Id { get; set; }
[ForeignKey("Id")]
public UserProfile UserProfile { get; set; }
}
Shared Primary Key with two-way navigation
If you want to navigate from UserProfile to Person you have more work to do. Simply adding public virtual Person Person { get; set; } to UserProfile will give you an error:
Unable to determine the principal end of an association between the types 'Test.Models.UserProfile' and 'Test.Models.Person'. The principal end of this association must be explicitly configured using either the relationship fluent API or data annotations.
So, we fix it with [Required] on the Person.UserProfile property (Person requires UserProfile). This gives the same migration as before.
// tested in EF 5 and MVC 4.5.
[Table("UserProfile")]
public class UserProfile {
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public int UserId { get; set; }
public string UserName { get; set; }
[ForeignKey("UserId")]
public virtual Person Person { get; set; }
}
[Table("Person")] // not required, added for clarity in sample code
public class Person {
[Key]
public int UserId { get; set; }
[ForeignKey("UserId")]
[Required]
public virtual UserProfile UserProfile { get; set; }
}
Again, this works if you use Id for Person instead of UserId:
public class Person {
[Key]
public int Id { get; set; }
[ForeignKey("Id")]
[Required]
public virtual UserProfile UserProfile { get; set; }
}
[Table("UserProfile")]
public class UserProfile
{
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public int UserId { get; set; }
public string UserName { get; set; }
public virtual Person Person {get;set;}
}
public class Person
{
public int Id { get; set; }
public int UserProfileUserId { get; set; } //Foreign Key
public virtual UserProfile UserProfile { get; set; }
}
If you want to create a one-to-one relationship the first thing you must clarify is what is the principal and what the dependent entity in this relationship. Can a Person exist without UserProfile or can a UserProfile exist without Person?
Because you have started to apply a [ForeignKey] attribute in Person I am assuming now that Person is the dependent, i.e. it cannot exist without UserProfile.
Correct application of the [ForeignKey] attribute would then be:
public class Person
{
[ForeignKey("UserProfile")]
public int Id { get; set; }
public UserProfile UserProfile { get; set; }
}
I am not sure if that is sufficient because you don't have a Person navigation property in UserProfile. If it doesn't work add this property to UserProfile:
public Person Person { get; set; }
If you don't want to have such a navigation property you can't avoid Fluent API:
modelBuilder.Entity<Person>()
.HasRequired(p => p.UserProfile)
.WithOptional();
I an fairly new to MVC, and have created an MVC4 application using EF-database-first. The database does not contain foreign key definitions and I can't add them (I don't own the database). Here are two example classes from the database:
public partial class Allocation
{
public int AllocID { get; set; }
public int DeptID { get; set; }
public decimal AllocationPercent { get; set; }
}
public partial class Department
{
public int DeptID { get; set; }
public string DeptName { get; set; }
public string Account { get; set; }
}
The default Allocation Index page shows the department ID. I want to show the department name instead. How can I do this without navigation properties?
I tried
public class AllocationController : Controller
{
private Entities db = new Entities();
//
// GET: /Allocation/
public ActionResult Index()
{
return View(db.Allocation.Include(d => d.DeptID).ToList());
}
...
but this gives an error ("A specified Include path is not valid. The EntityType 'TESTModel.Allocation' does not declare a navigation property with the name 'DeptID'.")...
I'm not sure how to code eager-loading or explicit-loading without navigation properties either, which prompted this question. Efficiency-wise, I don't believe it matters which way I load the related information, so any help in any direction would be appreciated.
The database does not have to have definitions, as long as the fields are there and the entities have been placed in the database with referential integrity in mind. All you need to do is let entity framework know about the relationship. This is done with the virtual keyword to create "Navigational Properties".
public partial class Allocation
{
public int AllocID { get; set; }
public int DeptID { get; set; }
public decimal AllocationPercent { get; set; }
public virtual Department Department { get; set; } /* this is your nav property */
}
public partial class Department
{
public int DeptID { get; set; }
public string DeptName { get; set; }
public string Account { get; set; }
}
Now you can do:
db.Allocation.Include(a => a.Department).ToList()
There may be an error which requires you to use a foreign key definition (although I do not think so). If this is the case, you will need to decorate your navigation property like this
[ForeignKey("DeptID")]
public virtual Department Department { get; set; }
You may also try it this way:
public int AllocID { get; set; }
[ForeignKey("Department")]
public int DeptID { get; set; }
public decimal AllocationPercent { get; set; }
public virtual Department Department { get; set; }
With navigation properties, Travis J's answer is what you need.
If you don't want to use navigation properties, assuming your DB context has a set called Departments, you could do smth like this:
var deptId = db.Allocation.DeptID;
var departments = db.Departments.Where(p => p.DeptID == deptId);
return View(departments.ToList());
I have a problem using QBE with NHibernate. I have a one-to-one relationship between a Person class and an Employee.
public class Person
{
public virtual Employee Employee { get; set; }
public virtual int Age { get; set; }
public virtual string Forename { get; set; }
public virtual string Surname { get; set; }
public virtual int PersonID { get; set; }
}
public class Employee
{
public virtual int PersonID { get; set; }
public virtual string PayRollNo { get; set; }
public virtual int Holidays { get; set; }
public virtual Person Person { get; set; }
}
As an example, I want to get all Employees where Employee.Forename="John" and Employee.Person.PayRollNo = "231A". I was wondering if I could use Query By Example to do this?
I have not been able to find a definitive "no" but I haven't been able to get this work. I've found that QBE is promising but unfortunately not very useful due to the following limitations:
Cannot query related objects.
Requires public parameterless constructor.
Initialized properties are included in query unless specifically excluded using ExcludeProeprty. For example, bool properties are restricted to false in the where clause, DateTime as DateTime.MinValue. This makes the query very brittle because class modifications may have bad side effects.