I have a many to many relationship mapping, and the mapping table has an additional field. I created the ApplicationDbContext as below:
public virtual DbSet<Country> Countries { get; set; }
public virtual DbSet<Region> Regions { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<CountryRegionMapping>()
.HasKey(um => um.CountryRegionMappingId)
.ToTable("CountryRegionMapping");
modelBuilder.Entity<CountryRegionMapping>()
.HasRequired(um => um.Region).WithMany(g => g.CountryMappings)
.HasForeignKey(um => um.RegionId);
modelBuilder.Entity<CountryRegionMapping>()
.HasRequired(um => um.Country).WithMany(g => g.RegionMappings)
.HasForeignKey(um => um.CountryId);
base.OnModelCreating(modelBuilder);
}
I was refering this link to create the Many-to-Many relationship having an extra field in the mapping table.
The entity classes are :
public class Country
{
public int Id { get; set; }
public string SystemOneName { get; set; }
public string SystemTwoName { get; set; }
public virtual ICollection<CountryRegionMapping> RegionMappings { get; set; }
}
public class Region
{
public int Id { get; set; }
public string SystemOneName { get; set; }
public string SystemTwoName { get; set; }
public virtual ICollection<CountryRegionMapping> CountryMappings { get; set; }
}
public class CountryRegionMapping
{
public int CountryRegionMappingId { get; set; }
public int CountryId { get; set; }
public virtual Country Country { get; set; }
public int RegionId { get; set; }
public virtual Region Region { get; set; }
public bool CheckField { get; set; }
}
When I try to access the Country or Region tables I can simply access it through the code as below using dbcontext.Regions
ApplicationDbContext db = new ApplicationDbContext();
db.Regions.SingleOrDefault(r => r.Id == Id);
But when I try to access the "CountryRegionMapping" entity I cannot access through a code as db.CountryRegionMapping
Why is this not available in the Db Context. How can I access this entity in the middle of a Many-to-Many relationship.
If you want to access the middle-mapping entities directly, add those as a DbSet on your context, along with the other ones:
public virtual DbSet<CountryRegionMapping> CountryRegionMappings { get; set; }
public virtual DbSet<Country> Countries { get; set; }
public virtual DbSet<Region> Regions { get; set; }
Then you can access them same as you access Countries, or Regions:
ApplicationDbContext db = new ApplicationDbContext();
db.CountryRegionMappings//.SingleOrDefault, etc.
Related
In my regular .NET Framework application, I was using EF 6.x and was also using some Inheritance, specifically:
PurchaseOrder.cs and SaleOrder.cs both inherit from Order.cs
And in the OnModelCreating() on my context class inheriting from IdentityDbContext, I was doing:
modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
This used to work, but now I am moving my application to .NET Core 2.0 and I am using EF Core. What achieves the same thing in EF Core? Because right now I am getting the error:
System.Data.SqlClient.SqlException (0x80131904): Introducing FOREIGN KEY constraint 'FK_Order_Business_CustomerId' on table 'Order' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.
UPDATE
Here's the code after Ahmar's answer. In my context class, I have:
protected override void OnModelCreating(ModelBuilder builder)
{
base.OnModelCreating(builder);
builder.HasDefaultSchema("PD");
builder.Entity<Customer>()
.HasMany(c => c.SaleOrders)
.WithOne(e => e.Customer)
.OnDelete(DeleteBehavior.SetNull);
builder.Entity<Supplier>()
.HasMany(po => po.PurchaseOrders)
.WithOne(e => e.Supplier)
.OnDelete(DeleteBehavior.SetNull);
builder.Entity<PurchaseOrder>()
.HasMany(li => li.LineItems)
.WithOne(po => po.PurchaseOrder)
.OnDelete(DeleteBehavior.SetNull);
builder.Entity<SaleOrder>()
.HasMany(li => li.LineItems)
.WithOne(po => po.SaleOrder)
.OnDelete(DeleteBehavior.SetNull);
}
And as far the Entities, they are:
public abstract class Business : IEntity
{
protected Business()
{
CreatedOn = DateTime.UtcNow;
}
public int Id { get; set; }
public string Name { get; set; }
public string TaxNumber { get; set; }
public string Description { get; set; }
public string Phone { get; set; }
public string Website { get; set; }
public string Email { get; set; }
public bool IsDeleted { get; set; }
public DateTime CreatedOn { get; set; }
public DateTime? ModifiedOn { get; set; }
public ICollection<Address> Addresses { get; set; } = new List<Address>();
public ICollection<Contact> Contacts { get; set; } = new List<Contact>();
}
[Table("Customers")]
public class Customer : Business
{
public decimal AllowedCredit { get; set; }
public decimal CreditUsed { get; set; }
public int NumberOfDaysAllowedToBeOnMaxedOutCredit { get; set; }
public ICollection<SaleOrder> SaleOrders { get; set; }
}
[Table("Suppliers")]
public class Supplier : Business
{
public ICollection<PurchaseOrder> PurchaseOrders { get; set; }
}
public abstract class Order : IEntity
{
protected Order()
{
Date = DateTime.UtcNow;
CreatedOn = DateTime.UtcNow;
}
public int Id { get; set; }
public DateTime Date { get; set; }
public decimal ShippingCost { get; set; }
public Currency ShippingCurrency { get; set; }
public decimal ShippingConversionRate { get; set; }
public bool IsDeleted { get; set; }
public DateTime CreatedOn { get; set; }
public DateTime? ModifiedOn { get; set; }
public ICollection<Invoice> Invoices { get; set; }
public ICollection<Note> Notes { get; set; }
}
[Table("PurchaseOrders")]
public class PurchaseOrder : Order
{
public int SupplierOrderNumber { get; set; }
public PurchaseOrderStatus Status { get; set; }
public decimal Vat { get; set; }
public decimal ImportDuty { get; set; }
public int SupplierId { get; set; }
public Supplier Supplier { get; set; }
public ICollection<PurchaseOrderLineItem> LineItems { get; set; }
}
[Table("SaleOrders")]
public class SaleOrder : Order
{
public decimal AmountToBePaidOnCredit { get; set; }
public SaleOrderStatus Status { get; set; }
public ICollection<SaleOrderLineItem> LineItems { get; set; }
public int CustomerId { get; set; }
public Customer Customer { get; set; }
}
So after doing what Ahmar suggested, I still get the same error when I do update-database.
You need to configure cascade delete behavior on each entity in .Net Core EF.
The Entity Framework Core Fluent API OnDelete method is used to specify the action which should take place on a dependent entity in a relationship when the principal is deleted.
The OnDelete method takes a DeleteBehavior enum as a parameter:
Cascade - dependents should be deleted
Restrict - dependents are
unaffected
SetNull - the foreign key values in dependent rows should
update to NULL
Example:
public class Company
{
public int Id { get; set; }
public string Name { get; set; }
public ICollection<Employee> Employees { get; set; }
}
public class Employee
{
public int Id { get; set; }
public string Name { get; set; }
public int? CompanyId { get; set; }
public Company Company { get; set; }
}
protected override void OnModelCreating(Modelbuilder modelBuilder)
{
modelBuilder.Entity<Company>()
.HasMany(c => c.Employees)
.WithOne(e => e.Company).
.OnDelete(DeleteBehavior.SetNull);
}
When deleting the Company, it will set CompanyId property in Employee table to null.
Get more detail at Configuring One To Many Relationships
PS. Please make sure your all referencing properties should be null able so, EF Core can set them null on delete. like CompanyId in about example.
I want to implement one-to-many relationship with EF6. Table User can handle many Friends, i can implement that with map table:
--TABLE USERS:
Id
--TABLE USER_MAP:
UserOwnerId
UserFriendId
But how to implement that with EF6?
Here is my entity User:
public class User
{
...
public virtual List<User> Friends { get; set; }
...
}
You can use something like this
// Relationships
HasRequired(t => t.User)
.WithMany(t => t.Friends)
.HasForeignKey(d => d.UserId);
https://msdn.microsoft.com/en-us/data/hh134698.aspx
One-to-Many relationship using DataAnnotations:
public class User
{
public User() { }
public int UserId { get; set; }
public string Name { get; set; }
public virtual Friends friends { get; set; }
}
public class Friends
{
public Friends()
{
Users = new List<User>();
}
public int FriendId { get; set; }
public string Name { get; set; }
public virtual ICollection<User> Users { get; set; }
}
you can defined in Code first like that:
1) Fluent API:
public class Student
{
public Student() { }
public int StudentId { get; set; }
public string StudentName { get; set; }
public virtual Standard Standard { get; set; }
}
public class Standard
{
public Standard()
{
Students = new List<Student>();
}
public int StandardId { get; set; }
public string Description { get; set; }
public virtual ICollection<Student> Students { get; set; }
}
Fleut Api:
in your DbContext:
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
//one-to-many
modelBuilder.Entity<Student>()
.HasRequired<Standard>(s => s.Standard)
.WithMany(s => s.Students);
}
virtual keyword is only for Lazy loading you can remove it if you do not need it
2) Code first:
public class Student
{
public Student()
{
Students= new List<Student>();
}
public int StundendId{ get; set; }
public string StudentName { get; set; }
public int? SharedStudentId{ get; set; }
[ForeignKey("SharedStudentId")]
public Student SharedStudent{ get; set; }
public virtual ICollection<Student> SharedStudents{ get; set; }
}
Here's the problem. I have table User which have quite a few fields. What I want to do is split this table into multiple entities like this:
User
-> GeneralDetails
-> CommunicationDetails
-> Address
etc.
All goes well when extracting some fields from User into GeneralDetails. However, when I try to do the same thing for CommunicationDetails EF blows up and require to establish one-to-one relationship between GeneralDetails and CommunicationDetails.
Sample entities definition:
public class User {
public int UserId { get; set; }
public string SomeField1 { get; set; }
public int SomeField2 { get; set; }
public virtual GeneralDetails GeneralDetails { get; set; }
public virtual CommunicationDetails CommunicationDetails { get; set; }
public virtual Address Address { get; set; }
}
public class GeneralDetails {
[Key]
public int UserId { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string Email { get; set; }
public virtual User User { get;set; }
}
public class CommunicationDetails {
[Key]
public int UserId { get; set; }
public string Phone { get; set; }
public string DeviceToken { get; set; }
public virtual User User { get;set; }
}
public class Address {
[Key]
public int UserId { get; set; }
public string City { get; set; }
public string Country { get; set; }
public string Street { get; set; }
public virtual User User { get;set; }
}
Sample mapping:
modelBuilder.Entity<User>().
HasRequired(user => user.GeneralDetails).
WithRequiredPrincipal(details => details.User);
modelBuilder.Entity<User>().
HasRequired(user => user.CommunicationDetails).
WithRequiredPrincipal(details => details.User);
modelBuilder.Entity<User>().
HasRequired(user => user.Address).
WithRequiredPrincipal(details => details.User);
modelBuilder.Entity<User>().ToTable("Users");
modelBuilder.Entity<GeneralDetails>().ToTable("Users");
modelBuilder.Entity<Address>().ToTable("Users");
Why on earth EF want this relationship? Is there any way this could be solved?
The correct way to actually do this is by Complex Types rather than entities. Its actually a more common problem than you think.
public class MyDbContext : DbContext
{
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelbuilder.ComplexType<CommunicationDetails>();
modelbuilder.ComplexType<GeneralDetails>();
modelbuilder.ComplexType<Address>();
modelbuilder.Entity<User>().ToTable("Users");
}
}
I'm using CodeFirst for my devemopment. For all model 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 need to get User information when I write objEmployee.CreatedUser
Thanks.
public class CommonFields
{
public int Status { get; set; }
public DateTime CreatedOn { get; set; }
public int? CreatedById { get; set; }
public virtual User CreatedBy { get; set; }
public DateTime ModifiedOn { get; set; }
public virtual User ModifiedBy { get; set; }
public int? ModifiedById { get; set; }
}
and you have to define relations for all derived entities in your DbContext
protected override void OnModelCreating(DbModelBuilder mb)
{
mb.Entity<User>().HasOptional(x => x.CreatedBy).WithMany().HasForeignKey(x => x.CreatedById).WillCascadeOnDelete(false);
mb.Entity<User>().HasOptional(x => x.ModifiedBy).WithMany().HasForeignKey(x => x.ModifiedById).WillCascadeOnDelete(false);
mb.Entity<Employee>().HasOptional(x => x.CreatedBy).WithMany().HasForeignKey(x => x.CreatedById).WillCascadeOnDelete(false);
mb.Entity<Employee>().HasOptional(x => x.ModifiedBy).WithMany().HasForeignKey(x => x.ModifiedById).WillCascadeOnDelete(false);
}
EDIT:
Or you could use TPH. Then your model creating look like this
protected override void OnModelCreating(DbModelBuilder mb)
{
mb.Entity<CommonFields>().
.Map(x => x.ToTable("Users"))
.Map<User>(x => x.Requires("__type").HasValue(1)
.Map<Employee>(x => x.Requires("__type").HasValue(2);
mb.Entity<CommonFields>().HasOptional(x => x.CreatedBy).WithMany().HasForeignKey(x => x.CreatedById).WillCascadeOnDelete(false);
mb.Entity<CommonFields>().HasOptional(x => x.ModifiedBy).WithMany().HasForeignKey(x => x.ModifiedById).WillCascadeOnDelete(false);
}
I have two classes, the Group class has a many to many relationship with the User class (representing the groups a user belongs to) and then the group also has a relationship of one to many with the user class (representing the owner of a group).
How can I map this?
public class User
{
public int Id { get; set; }
public string Avatar { get; set; }
public string Name { get; set; }
public string Message { get; set; }
public virtual ICollection<Group> OwnedGroups { get; set; }
public virtual ICollection<Group> Groups { get; set; }
}
public class Group
{
public int Id { get; set; }
public DateTime CreateDate { get; set; }
public DateTime ModifyDate { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public bool System { get; set; }
public int ViewPolicy { get; set; }
public int JoinPolicy { get; set; }
public string Avatar { get; set; }
public int Order { get; set; }
public int GroupType { get; set; }
public virtual User Owner { get; set; }
public virtual ICollection<User> Members { get; set; }
}
tks in advance!
I would use fluent API:
public class Context : DbContext
{
public DbSet<User> Users { get; set; }
public DbSet<Group> Groups { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Entity<User>()
.HasMany(u => u.Groups)
.WithMany(g => g.Members);
modelBuilder.Entity<User>()
.HasMany(u => u.OwnedGroups)
.WithRequired(g => g.Owner)
.WillCascadeOnDelete(false);
}
}
It should also be possible with Data annotations:
public class User
{
...
[InverseProperty("Owner")]
public virtual ICollection<Group> OwnedGroups { get; set; }
[InverseProperty("Members")]
public virtual ICollection<Group> Groups { get; set; }
}
public class Group
{
...
[InverseProperty("OwnedGroups")]
public virtual User Owner { get; set; }
[InverseProperty("Groups")]
public virtual ICollection<User> Members { get; set; }
}
InverseProperty is not needed on both sides of relation but it does definition clearer.