Dear Entity experts and others,
I have the following entities,
Base class Individual:
public abstract class Individual
{
[Key]
public int IndividualID { get; set; }
... other properties
}
Yogi:
[Table("Yogis")]
public class Yogi : Individual
{
public string Firstname { get; set; }
public string Lastname { get; set; }
public DateTime Birthdate { get; set; }
}
Customer:
[Table("Customers")]
public class Customer : Individual
{
public string Name { get; set; }
[ForeignKey("VATID")] // tried with and without
public virtual VAT VAT { get; set; }
}
VAT:
public class VAT
{
[Key]
public int VATID { get; set; }
[Required]
public virtual Customer VATHolder { get; set; }
... other properties
}
DbContext:
public DbSet<Individual> Individuals { get; set; }
public DbSet<VAT> VATS { get; set; }
So the above creates a table VAT where there VATID is 2 to start with which should be 1 instead, I don't understand why this happens, this should be 1, isn't it? Also, there is no reference anywhere in any table that references Customer & VAT, how can I create a separate table VAT_Customer where you have a VATID & CustomerID ?
This is how i create and insert the entity Customer:
VAT vat = new VAT("123456789");
DataBaseHandler.InsertIndividual(new Customer("Customer name", vat,...));
Insert Function:
public static void InsertIndividual(Individual individual)
{
using (MyDbContext ctx = new MyDbContext())
{
ctx.Individuals.Add(individual);
ctx.SaveChanges();
}
}
I have tried several ways (EXAMPLES HERE) but I prefer the TPT way, having a separate view of any entity or relations between entities. What am I doing wrong and how would I achieve the desired result? Let me know if I can clarify anything. Thank you in advance for any help or suggestions!
Kind regards!
Your ForeignKey placement should look something like this if you wanna have 1:1 Relationship :
enter code here
[ForeignKey("VAT")]
public virtual int VATId { get; set; }
public virtual VAT VAT { get; set; }
Name in the ForeignKey is same as your class.
hope this can help
Related
I am having issues trying to map two fields that are foreign keys into the same table. The use case is for a modifier and creator. My class already has the Ids, and then I wanted to add the full User object as virtual.
I am using a base class so that each of my tables have the same audit fields:
public class Entity
{
public long? ModifiedById { get; set; }
public long CreatedById { get; set; } = 1;
[ForeignKey("CreatedById")]
public virtual User CreatedByUser { get; set; }
[ForeignKey("ModifiedById")]
public virtual User ModifiedByUser { get; set; }
}
The child class is very simple:
public class CircleUserSubscription : Entity
{
[Required]
public long Id { get; set; }
public long SponsorUserId { get; set; }
[ForeignKey("SponsorUserId")]
public virtual User User { get; set; }
public long TestId { get; set; }
[ForeignKey("TestId")]
public virtual User Test { get; set; }
}
This is a standard junction table.
When I try to generate the migration, I am getting errors that I don't understand fully.
Unable to determine the relationship represented by navigation property 'CircleUserSubscription.User' of type 'User'. Either manually configure the relationship, or ignore this property using the '[NotMapped]' attribute or by using 'EntityTypeBuilder.Ignore' in 'OnModelCreating'.
I tried what this answer had, but the code is basically the same: https://entityframeworkcore.com/knowledge-base/54418186/ef-core-2-2---two-foreign-keys-to-same-table
An inverse property doesn't make sense since every table will have a reference to the user table.
For reference, here is the User entity:
public class User : Entity
{
public long Id { get; set; }
public string Username { get; set; }
public string Email { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
}
I am hoping you all can help me out, TIA :)
EDIT: One thing to note, all of this worked fine when the entity class was as follows:
public class Entity
{
public long? ModifiedById { get; set; }
public long CreatedById { get; set; } = 1;
}
It was only after I added the entity that things went awry.
I'm testing the following scenario (code below): create a shopping mall, with shops, with cashiers, with cash desks and persons operating it.
So I've created the following classes
Table Mall
Table Shop
Table CashDesk
Table Person
Basic classes with an ID and a name.
Then I need a derived class from Person being PersonCashier or PersonCustomer.
Since everything is related, I need to create intersection tables for the many to many scenarios.
I've created the following intersection tables:
The Mall contains shops: MallShop
The shop contains CashDesks: MallShopCashDesk
And the CashDesk containing cashiers: MallShopCashDeskPersonCashier
This just doesnt feel right. Can anyone help me out on a best practice
public class Mall
{
public int Id { get; set; }
[Required]
[MaxLength(100)]
public string Name { get; set; }
[Required]
public int NumberOfShopSpaces { get; set; }
}
public class Shop
{
public int Id { get; set; }
[Required]
[MaxLength(100)]
public string Name { get; set; }
}
public class CashDesk
{
public int Id { get; set; }
[Required]
public string Name { get; set; }
}
public class Person
{
public int Id { get; set; }
[Required]
public string FullName { get; set; }
[Required]
public string Gender { get; set; }
}
public class PersonCashier : Person
{
[Required]
public int ShopId { get; set; }
public virtual Shop Shop { get; set; }
}
These are the base classes. How should i add a shop to a mall, a cashdesk to a shop, and a cashier to a cashdesk? (i've tried alot but posting the code would make the question look like spaghetti)
If this is code first then EF will make the relationship tables for you. You just need to add the relationships in your classes.
Exactly what they should be is not clear from your description because it depends on what relationships you want; if you want a many-many between PersonCashier and CashDesk it would be like this:
public class CashDesk
{
public List<PersonCashier> Cashiers { get; set; }
}
public class PersonCashier : Person
{
public List<CashDesk> CashDesks { get; set; }
}
(not showing all the fields for brevity)
public class Mall
{
public int Id { get; set; }
[Required]
[MaxLength(100)]
public string Name { get; set; }
[Required]
public int NumberOfShopSpaces { get; set; }
List<Shop> CurrentShops { get; set; }
}
public class Shop
{
public int Id { get; set; }
[Required]
[MaxLength(100)]
public string Name { get; set; }
public List<CashDesk> CashDesks { get;set; }
}
I added the list of shops to the Mall class and CashDesks to Shops. This gives you a list of shops in the mall, and a list of cashdesks in each shop and you can follow this method for everything else you need.
If you have a database, you will have a Mall table and a Shop table.
The Shop table can have a Foreign Key to the Mall table, that's how you link them and this will work with the class structure at the top.
Or, you can have another table called MallShops where you have 2 fields, one being the MallID, the other the ShopID. This is called a Link table.
Both approaches will work with the second allowing a more complex structure with lots of Malls linked to Lots of Shops.
I would start with the database structure first, make sure you cover all you need, then you can do the classes etc in a way that makes sense. If you use something like EntityFramework then it will create all the classes for you once your database structure is ready.
I have a DbContext which I via the developer command prompt and creating a migrations schema turn in to my database. But if you look at the product object I have a dictionary object named Parts. That property does not get added to the Product table when the database is updated in the command prompt. I don't even know if it is possible what I am trying to do.
I want to add a table in the database named Parts and then add a foreign key to the Product table which connects the Parts dictionary object in the Product table, and the the new Parts table. Is this possible with Entity Framework Core?
public class ShoppingDbContext : IdentityDbContext<User>
{
public ShoppingDbContext(DbContextOptions options) : base(options)
{
}
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
base.OnConfiguring(optionsBuilder);
}
public DbSet<Product> Products { get; set; }
public DbSet<Order> Orders { get; set; }
}
public class Product
{
public int ProductId { get; set; }
public string ProductName { get; set; }
public double Price { get; set; }
public int CategoryId { get; set; }
Dictionary<string, Part> Parts { get; set; }
}
EF Core can't currently map a dictionary property directly. If you want to create an association between Products and Parts, then define each of them as an entity. You can then create navigation properties between them--a reference from Part to the Product which it belongs, and a collection of Parts on Product. For example:
public class Product
{
public int ProductId { get; set; }
public string ProductName { get; set; }
public double Price { get; set; }
public int CategoryId { get; set; }
public ICollection<Part> Parts { get; set; }
}
public class Part
{
public int PartId { get; set; }
public int ProductId { get; set; }
public Product Product { get; set;}
}
Part also defines a property ProductId that acts as the FK to the Product entity. You don't need to add that property--EF will simulate it for you if you don't want it, but usually it is easier to deal with entities if the FK is mapped to a property.
Relationships are tracked through object references instead of foreign key properties. This type of association is called an independent association.
More Details Here:
https://msdn.microsoft.com/en-us/data/jj713564.aspx
Sample code:
public partial class Product
{
public Product()
{
this.Parts = new HashSet<Part>();
}
public int ProductId { get; set; }
public string ProductName { get; set; }
public double Price { get; set; }
public int CategoryId { get; set; }
public virtual ICollection<Part> Parts { get; set; }
}
Basically like what Arthur said, EF Core does not support it yet.
However, another way is to create a composite table should you want to or if it's viable for your use.
Here's a simple example:
// -------------- Defining BrandsOfCategories Entity --------------- //
modelBuilder.Entity<BrandCategory>()
.HasKey(input => new { input.BrandId, input.CatId })
.HasName("BrandsOfCategories_CompositeKey");
modelBuilder.Entity<BrandCategory>()
.Property(input => input.DeletedAt)
.IsRequired(false);
// -------------- Defining BrandsOfCategories Entity --------------- //
public class BrandCategory
{
public int CatId { get; set; }
public int BrandId { get; set; }
public DateTime? DeletedAt { get; set; }
public Category Category { get; set; }
public Brands Brand { get; set; }
}
The DeletedAt is optional of course. This handles M-M Relationships.
I had the same issue, I resolved it by removing the keyword virtual on the navigation properties and with in the ApplicatinDbContext
I am wondering if anyone could advise me on how to accomplish the below using code first in EF6
If I add the Table_3 as a List on to Table_1 & Table_2 in my entities. EF automatically generates a foreign key column for both tables in Table_3 instead of recognizing that they are of the same type.
My model classes are set as follows.
public interface IParent
{
int ID { get; set; }
List<Table_3> Children { get; set; }
}
public class Table_1 : IParent
{
[Key]
public int ID { get; set; }
public string Name { get; set; }
public virtual List<Table_3> Children { get; set; }
}
public class Table_2 : IParent
{
[Key]
public int ID { get; set; }
public string Name { get; set; }
public virtual List<Table_3> Children { get; set; }
}
public class Table_3
{
[Key]
public int ID { get; set; }
public int ParentID { get; set; }
[ForeignKey("ParentID")]
public virtual IParent Parent { get; set; }
}
EF code first generates the below
Edit
Just to let anyone having the same problems know
I have now resolved this by changing the IParent interface to an abstract class
my classes now look like the following
[Table("ParentBase")]
public abstract class ParentBase
{
[Key]
public int ID { get; set; }
public List<Table_3> Children { get; set; }
}
[Table("Table_1")]
public class Table_1 : ParentBase
{
public string Name { get; set; }
}
[Table("Table_2")]
public class Table_2 : ParentBase
{
public string Name { get; set; }
}
[Table("Table_3")]
public class Table_3
{
[Key]
public int ID { get; set; }
public int ParentID { get; set; }
[ForeignKey("ParentID")]
public virtual ParentBase Parent { get; set; }
}
with a table arrangement of
this will work although it would have been nicer if the original could have been met.
I had this problem too, and I used abstract class instead of interface from the beginning.
The problem for mine was my table_3 have two navigation properties:
one is public virtual Table_1, another is public virtual Table_2, and then EF just provisioned these extra foreign key columns,
I merged the two navigation properties into one to
public virtual parentbase {get;set;}. And then it worked. Hope this helps.
Side Note,Would suggest to add virtual keyword on public List Children { get; set; } in parentbase class, because in your previous example , it was already like that.
Thanks for posting this, i came across this issue too.
You can also do like the following where you make a 1 to many relationship between Table_1 and Table_2 with Table_3 respectively:
modelBuilder.Entity<Table_3>().HasOptional(/*Nav Prop*/).WithMany(m => m.Table_3s).HasForeignKey(f => f.ParentId).WillCascadeOnDelete(false);
modelBuilder.Entity<Table_3>().HasOptional(/*Nav Prop*/).WithMany(m => m.Table_3s).HasForeignKey(f => f.ParentId).WillCascadeOnDelete(false);
Let me know if anymore clarification is required.
I am getting the following exception:
I have gone through many posts here, here and here. But no post suggests proper solution to the problem. I want to know how can this situation be tackled practically.
My Models and Contexts are as follows:
public class Context : DbContext
{
public Context() : base("DefaultConnection")
{
}
public DbSet<Student> Students { get; set; }
public DbSet<Course> Courses { get; set; }
public DbSet<Staff> Staffs { get; set; }
}
public class Student
{
public int StudentId { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
[Required]
public virtual Course Course { get; set; }
[Required]
public virtual Staff Staff { get; set; }
}
public class Staff
{
public int StaffId { get; set; }
public string Name { get; set; }
public string Contact { get; set; }
}
public class Course
{
public int CourseId { get; set; }
public string CourseName { get; set; }
[Required]
public virtual Staff Staff { get; set; }
}
I am getting this exception on the line :
context.Students.Add(student);
of the following code:
public void AddStudent()
{
Student student = new Student();
student.FirstName = "Bruce";
student.LastName = "Wayne";
student.Course = new Course();
student.Course.CourseName = "CSE";
student.Course.Staff = new Staff();
student.Course.Staff.Name = "Albert";
student.Course.Staff.Contact = "1234567890";
context.Students.Add(student);
context.Courses.Add(student.Course);
context.SaveChanges();
Console.WriteLine("Student , Course, Staff Added");
}
I had asked this question some time back. This should help you out.
EF Code First giving problems in foreign keys
Reference reading here
http://weblogs.asp.net/manavi/archive/2011/05/01/associations-in-ef-4-1-code-first-part-5-one-to-one-foreign-key-associations.aspx
The main part to look for in the article is "What's a Multiple Cascade Path Anyway?"
To solve the problem practically you need to identify which path do you want the cascade delete to be turned on. For e.g. If the a staff gets deleted does the course also get deleted or does it remain ?
Disabling cascading deletes for that entity should solve your issue. If you want a cascading delete for this set of entities, do it manually. It can't be done automatically because when there's a cycle there's no way to determine when to stop.