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; }
}
Related
I'm trying to create a many to many relation in the Fluent API with Ef Core 6 but i am having trouble understanding how to do so.
I've looked around here in stackoverflow but couldn't understand this relation and how to reproduce it in my code.
I have a table in my SQL database called People:
People.cs:
public class People : PeopleBase
{
public People()
{
RegistrationList = new HashSet<Registration>();
}
public virtual ICollection<Registration> RegistrationList { get; set; }
public virtual User User { get; set; }
public virtual ActivityGroup ActivityGroup { get; set; }
}
PeopleBase.cs:
public abstract class PeopleBase: ModelBase
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public Guid PeopleId { get; set; }
public Guid? UserId { get; set; }
public Guid? ActivityGroupId { get; set; }
public string Code { get; set; }
public string Name { get; set; }
public string Surname { get; set; }
public PeopleActiveType Active { get; set; }
}
And then i have another table called ActivityGroup:
ActivityGroup.cs:
public class ActivityGroup : ActivityGroupBase
{
public ActivityGroup()
{
PeopleList = new HashSet<People>();
ActivityList = new HashSet<Activity>();
}
public ICollection<People> PeopleList { get; set; }
public ICollection<Activity> ActivityList { get; set; }
}
ActivityGroupBase.cs:
public abstract class ActivityGroupBase : ModelBase
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public Guid ActivityGroupId { get; set; }
[Required]
[StringLength(20)]
public string Name { get; set; }
public StatusRecord Status { get; set; }
}
How would i do the mapping in the modelBuilder given that:
ActivityGroupId is the foreing key in the People database, pointing to the other table
One PeopleId can have multiple (many) ActivityGroupId
One ActivityGroupId can be assigned to multiple people.
What i've done so far:
modelBuilder.Entity<People>()
.HasOne(x => x.ActivityGroup)
.WithMany(x => x.PeopleList)
.HasForeignKey(x => x.ActivityGroupId);
Wouldn't i have to do this instead?
modelBuilder.Entity<People>()
.Hasmany(x => x.ActivityGroupList) //this is a ICollection<ActivityGroup> inside People class
.WithMany(x => x.PeopleList)
.HasForeignKey(x => x.ActivityGroupId); // this is not recognized by Ef Core
Can anyone help me please?
There are two main approaches for many-to-many relationships - with implicit junction table:
public class People : PeopleBase
{
// ...
public virtual List<Activity> Activities { get; set; }
}
public class Activity // : ...
{
// ...
public virtual List<People> PeopleList { get; set; }
}
modelBuilder.Entity<People>()
.HasMany(x => x.Activities)
.WithMany(x => x.PeopleList);
Or with explicit one:
public class People
{
// ...
public ICollection<PeopleActivity> PeopleActivities { get; set; }
}
public class Activity
{
// ...
public virtual ICollection<PeopleActivity> PeopleActivities { get; set; }
}
public class PeopleActivity
{
public Guid ActivityId { get; set; }
public Guid PeopleId { get; set; }
public Activity Activity { get; set; }
public People People { get; set; }
}
modelBuilder.Entity<PeopleActivity>()
.HasOne(pt => pt.People)
.WithMany(t => t.PeopleActivities)
.HasForeignKey(pt => pt.PeopleId);
Also maybe it worth changing entity name from People to Person (you can change table name with .ToTable("People") call)?
I want to create a one-to-many relationship using EF 6 using a code-first approach.
Let's take simple and classical example. I have two entities Invoice and UserApplication which have a one-to-many relationship:
I also want to have an UpdatedById relationship with the same ApplicationUser table, to be able to show the names in the UI of who added the record and who modified it.
public partial class ApplicationUser : IdentityUser
{
public string FirstName { get; set; };
public string LastName { get; set; };
}
public virtual List<Invoice> Invoices { get; set; }
public class Invoice
{
public int Id { get; set; }
public string Details { get; set; }
public string CreatedById { get; set; }
public string UpdatedById { get; set; }
}
public virtual ApplicationUser CreatedBy { get; set; }
builder.Entity<Invoice>()
.HasOne(f => f.CreatedBy)
.WithMany(mu => mu.Invoices)
.HasForeignKey(f => f.CreatedById);
If you want Navigation Properties on Application user for these relationships, you would need to create and configure seperate ones.
eg
using Microsoft.EntityFrameworkCore;
using System.Linq;
using System;
using System.Collections.Generic;
namespace EfCore6Test
{
public partial class ApplicationUser //: IdentityUser
{
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public virtual ICollection<Invoice> InvoicesCreated { get; } = new HashSet<Invoice>();
public virtual ICollection<Invoice> InvoicesLastUpdated { get; } = new HashSet<Invoice>();
}
public class Invoice
{
public int Id { get; set; }
public string Details { get; set; }
public int CreatedById { get; set; }
public int UpdatedById { get; set; }
public virtual ApplicationUser CreatedBy { get; set; }
public virtual ApplicationUser LastUpdatdBy { get; set; }
}
public class Db: DbContext
{
public DbSet<Invoice> Invoices{ get; set; }
public DbSet<ApplicationUser> Users{ get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Invoice>()
.HasOne(f => f.CreatedBy)
.WithMany(mu => mu.InvoicesCreated)
.HasForeignKey(f => f.CreatedById)
.OnDelete(DeleteBehavior.Restrict);
modelBuilder.Entity<Invoice>()
.HasOne(f => f.LastUpdatdBy)
.WithMany(mu => mu.InvoicesLastUpdated)
.HasForeignKey(f => f.UpdatedById)
.OnDelete(DeleteBehavior.Restrict);
base.OnModelCreating(modelBuilder);
}
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.UseSqlServer("Server=localhost;database=efCore6Test;Integrated Security=true;TrustServerCertificate=true", o => o.UseRelationalNulls(true))
.LogTo(Console.WriteLine, Microsoft.Extensions.Logging.LogLevel.Information);
base.OnConfiguring(optionsBuilder);
}
}
class Program
{
static void Main(string[] args)
{
{
using var db = new Db();
db.Database.EnsureDeleted();
db.Database.EnsureCreated();
}
}
}
}
Or simply omit the Navigation Properties on Application User.
In project I can have one User that can have many UserActivites. In my models I've set up their relationship as follows:
public class User
{
public int Id { get; set; }
public string UserName { get; set; }
public string FirstName { get; set; }
public string Surname { get; set; }
public string Email { get; set; }
//relationship mapping example
// delete these attributes and you'll cause a self referenceing loop error
[JsonIgnore]
[IgnoreDataMember]
public List<UserActivity> Activities { get; set; }
}
public class UserActivity
{
public int Id { get; set; }
public string UserName { get; set; }
public string Email { get; set; }
public string Project { get; set; }
public DateTime EntryDate { get; set; }
// relationship mapping
public User User { get; set; }
}
And in my repository class, I'm getting all my user activities this way:
public async Task<IEnumerable<UserActivity>> GetAll()
{
var result = await _context.UserActivities.Include(activity => activity.User).OrderByDescending(x => x.EntryDate).ToListAsync();
return result;
}
However, when I run my project, the User property of UserActivities is null. So I checked the Microsoft docs on EF Core relationships and updated my OnModelCreating method inside of my context to also do the mapping as follows:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<UserActivity>().ToTable("UserActivities").Property(x => x.Id).ValueGeneratedOnAdd();
modelBuilder.Entity<UserActivity>().ToTable("UserActivities").HasOne(x => x.User).WithMany();
modelBuilder.Entity<User>().ToTable("Users").Property(x => x.Id).ValueGeneratedOnAdd();
base.OnModelCreating(modelBuilder);
}
However, when I run the project again, my User property still isn't populated. I know this isn't a data issue as I have data inside of my User table and display that on a separate page.
I'm not sure what I'm doing wrong/missing with this. So any help would be appreciated
Try this code:
Your tables:
public partial class User
{
public User()
{
UserActivities = new HashSet<UserActivity>();
}
[Key]
public int Id { get; set; }
[Required]
public string UserName { get; set; }
[Required]
public string FirstName { get; set; }
[Required]
public string LastName { get; set; }
public string Email { get; set; }
[InverseProperty(nameof(UserActivity.User))]
public virtual ICollection<UserActivity> UserActivities { get; set; }
}
public partial class UserActivity
{
[Key]
public int Id { get; set; }
public int UserId { get; set; }
public string Project { get; set; }
public DateTime EntryDate { get; set; }
[ForeignKey(nameof(UserId))]
[InverseProperty("UserActivity")]
public virtual User User { get; set; }
}
dbcontext:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<UserActivity>(entity =>
{
entity.HasOne(d => d.User)
.WithMany(p => p.UserActivities)
.HasForeignKey(d => d.UserId)
.OnDelete(DeleteBehavior.ClientSetNull)
.HasConstraintName("FK_UserActivity_User");
});
OnModelCreatingPartial(modelBuilder);
}
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.
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");
}
}