Using Updatable Views with Entity Framework Code First - c#

I am learning to use Entity Framework (code first). Everything was going well until I realized I need to interact with an existing updatable view. I have confirmed the view can be updated in SSMS.
There are two entities involved: AppUser (Identity User) and FacilityView.
public class AppUser : IdentityUser
{
// additional props
public virtual ICollection<FacilityView> Facilities { get; set; }
}
public class FacilityView
{
[HiddenInput(DisplayValue=false)]
public int ID { get; set; }
public string Name { get; set; }
public string County { get; set; }
public string WebSiteURL { get; set; }
public bool IsActive { get; set; }
public virtual ICollection<AppUser> Users { get; set; }
}
I've used navigation properties to relate the two, thinking EF will build the join table when I run the next migration. I've read that EF treats views as read-only, so I tried to override this by creating my own EntityTypeConfiguration class:
public class FacilityViewConfiguration : EntityTypeConfiguration<FacilityView>
{
public FacilityViewConfiguration()
{
this.HasKey(t => t.ID);
this.ToTable("FacilityViews");
}
}
The configuration is referenced in my context class inside the OnModelCreating method.
public class AppIdentityDbContext : IdentityDbContext<AppUser>
{
public AppIdentityDbContext() : base("DbConn") { }
public DbSet<Facility> Facilities { get; set; }
public DbSet<FacilityView> FacilityDetails { get; set; }
static AppIdentityDbContext()
{
Database.SetInitializer<AppIdentityDbContext>(new DbConnInit());
}
public static AppIdentityDbContext Create()
{
return new AppIdentityDbContext();
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
// TRYING TO TRICK EF HERE
modelBuilder.Configurations.Add(new FacilityViewConfiguration());
}
}
When I add a migration, this is the resulting Up and Down:
public partial class UserFacilityJoinTable : DbMigration
{
public override void Up()
{
CreateTable(
"dbo.AppUserFacilityViews",
c => new
{
AppUser_ID = c.String(nullable: false, maxLength: 128),
FacilityViewsID = c.Int(nullable: false),
})
.PrimaryKey(t => new { t.AppUser_ID, t.FacilityViewsID })
.ForeignKey("dbo.AspNetUsers", t => t.AppUser_ID, cascadeDelete: true)
.ForeignKey("dbo.FacilityViews", t => t.FacilityViewsID, cascadeDelete: true)
.Index(t => t.AppUser_ID)
.Index(t => t.FacilityViewsID);
}
public override void Down()
{
DropForeignKey("dbo.AppUserFacilityViews", "FacilityViewsID", "dbo.FacilityViews");
DropForeignKey("dbo.AppUserFacilityViews", "AppUser_ID", "dbo.AspNetUsers");
DropIndex("dbo.AppUserFacilityViews", new[] { "FacilityViewsID" });
DropIndex("dbo.AppUserFacilityViews", new[] { "AppUser_ID" });
DropTable("dbo.AppUserFacilityViews");
}
}
It is attempting to create a new join table like I wanted, but when I run the Update-Database command, I get the following error:
Foreign key 'FK_dbo.AppUserFacilityViews_dbo.FacilityViews_FacilityViewsID' references object 'dbo.FacilityViews' which is not a user table.
Could not create constraint. See previous errors.
I thought I had tricked EF into treating the view like a table, but it's obviously not buying it. I'm wondering if I missed something or maybe taking the wrong approach. Any help will be greatly appreciated. I've been stuck here for a few days.


AFAIK you can't create a constraint to/from a view (even a materialized one, exception of index).
But you can model your context without database FK. You then have to handle the integrity at context or application level

Related

Introducing foreign key constraint asp.net problem [duplicate]

I've been wrestling with this for a while and can't quite figure out what's happening. I have a Card entity which contains Sides (usually 2) - and both Cards and Sides have a Stage. I'm using EF Codefirst migrations and the migrations are failing with this error:
Introducing FOREIGN KEY constraint 'FK_dbo.Sides_dbo.Cards_CardId' on
table 'Sides' may cause cycles or multiple cascade paths. Specify ON
DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY
constraints.
Here's my Card entity:
public class Card
{
public Card()
{
Sides = new Collection<Side>();
Stage = Stage.ONE;
}
[Key]
[Required]
public virtual int CardId { get; set; }
[Required]
public virtual Stage Stage { get; set; }
[Required]
[ForeignKey("CardId")]
public virtual ICollection<Side> Sides { get; set; }
}
Here's my Side entity:
public class Side
{
public Side()
{
Stage = Stage.ONE;
}
[Key]
[Required]
public virtual int SideId { get; set; }
[Required]
public virtual Stage Stage { get; set; }
[Required]
public int CardId { get; set; }
[ForeignKey("CardId")]
public virtual Card Card { get; set; }
}
And here's my Stage entity:
public class Stage
{
// Zero
public static readonly Stage ONE = new Stage(new TimeSpan(0, 0, 0), "ONE");
// Ten seconds
public static readonly Stage TWO = new Stage(new TimeSpan(0, 0, 10), "TWO");
public static IEnumerable<Stage> Values
{
get
{
yield return ONE;
yield return TWO;
}
}
public int StageId { get; set; }
private readonly TimeSpan span;
public string Title { get; set; }
Stage(TimeSpan span, string title)
{
this.span = span;
this.Title = title;
}
public TimeSpan Span { get { return span; } }
}
What's odd is that if I add the following to my Stage class:
public int? SideId { get; set; }
[ForeignKey("SideId")]
public virtual Side Side { get; set; }
The migration runs successfully. If I open up SSMS and look at the tables, I can see that Stage_StageId has been added to Cards (as expected/desired), however Sides contains no reference to Stage (not expected).
If I then add
[Required]
[ForeignKey("StageId")]
public virtual Stage Stage { get; set; }
public int StageId { get; set; }
To my Side class, I see StageId column added to my Side table.
This is working, but now throughout my application, any reference to Stage contains a SideId, which is in some cases totally irrelevant. I'd like to just give my Card and Side entities a Stage property based on the above Stage class without polluting the stage class with reference properties if possible... what am I doing wrong?

Because Stage is required, all one-to-many relationships where Stage is involved will have cascading delete enabled by default. It means, if you delete a Stage entity
the delete will cascade directly to Side
the delete will cascade directly to Card and because Card and Side have a required one-to-many relationship with cascading delete enabled by default again it will then cascade from Card to Side
So, you have two cascading delete paths from Stage to Side - which causes the exception.
You must either make the Stage optional in at least one of the entities (i.e. remove the [Required] attribute from the Stage properties) or disable cascading delete with Fluent API (not possible with data annotations):
modelBuilder.Entity<Card>()
.HasRequired(c => c.Stage)
.WithMany()
.WillCascadeOnDelete(false);
modelBuilder.Entity<Side>()
.HasRequired(s => s.Stage)
.WithMany()
.WillCascadeOnDelete(false);

I had a table that had a circular relationship with others and I was getting the same error. Turns out it is about the foreign key which was not nullable. If the key is not nullable the related object must be deleted, and circular relations don't allow that. So use nullable foreign key.
[ForeignKey("StageId")]
public virtual Stage Stage { get; set; }
public int? StageId { get; set; }

Anybody wondering how to do it in EF core:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
foreach (var relationship in modelBuilder.Model.GetEntityTypes().SelectMany(e => e.GetForeignKeys()))
{
relationship.DeleteBehavior = DeleteBehavior.Restrict;
}
..... rest of the code.....

I was getting this error for lots of entities when I was migrating down from an EF7 model to an EF6 version. I didn't want to have to go through each entity one at a time, so I used:
builder.Conventions.Remove<ManyToManyCascadeDeleteConvention>();
builder.Conventions.Remove<OneToManyCascadeDeleteConvention>();

You can set cascadeDelete to false or true (in your migration Up() method). Depends upon your requirement.
AddForeignKey("dbo.Stories", "StatusId", "dbo.Status", "StatusID", cascadeDelete: false);

In .NET Core I changed the onDelete option to ReferencialAction.NoAction
constraints: table =>
{
table.PrimaryKey("PK_Schedule", x => x.Id);
table.ForeignKey(
name: "FK_Schedule_Teams_HomeId",
column: x => x.HomeId,
principalTable: "Teams",
principalColumn: "Id",
onDelete: ReferentialAction.NoAction);
table.ForeignKey(
name: "FK_Schedule_Teams_VisitorId",
column: x => x.VisitorId,
principalTable: "Teams",
principalColumn: "Id",
onDelete: ReferentialAction.NoAction);
});

I had this issue also, I solved it instantly with this answer from a similar thread
In my case, I didn't want to delete the dependent record on key deletion. If this is the case in your situation just simply change the Boolean value in the migration to false:
AddForeignKey("dbo.Stories", "StatusId", "dbo.Status", "StatusID", cascadeDelete: false);
Chances are, if you are creating relationships which throw this compiler error but DO want to maintain cascade delete; you have an issue with your relationships.

I fixed this. When you add the migration, in the Up() method there will be a line like this:
.ForeignKey("dbo.Members", t => t.MemberId, cascadeDelete:True)
If you just delete the cascadeDelete from the end it will work.

Just for documentation purpose, to someone that comes on the future, this thing can be solved as simple as this, and with this method, you could do a method that disabled one time, and you could access your method normally
Add this method to the context database class:
protected override void OnModelCreating(DbModelBuilder modelBuilder) {
modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
}

In .NET Core I played with all upper answers - but without any success.
I made changes a lot in DB structure and every time added new migration attempting to update-database, but received the same error.
Then I started to remove-migration one by one until Package Manager Console threw me exception:
The migration '20170827183131_***' has already been applied to the database
After that, I added new migration (add-migration) and update-database successfully
So my suggestion would be: clear out all your temp migrations, until your current DB state.

public partial class recommended_books : DbMigration
{
public override void Up()
{
CreateTable(
"dbo.RecommendedBook",
c => new
{
RecommendedBookID = c.Int(nullable: false, identity: true),
CourseID = c.Int(nullable: false),
DepartmentID = c.Int(nullable: false),
Title = c.String(),
Author = c.String(),
PublicationDate = c.DateTime(nullable: false),
})
.PrimaryKey(t => t.RecommendedBookID)
.ForeignKey("dbo.Course", t => t.CourseID, cascadeDelete: false) // was true on migration
.ForeignKey("dbo.Department", t => t.DepartmentID, cascadeDelete: false) // was true on migration
.Index(t => t.CourseID)
.Index(t => t.DepartmentID);
}
public override void Down()
{
DropForeignKey("dbo.RecommendedBook", "DepartmentID", "dbo.Department");
DropForeignKey("dbo.RecommendedBook", "CourseID", "dbo.Course");
DropIndex("dbo.RecommendedBook", new[] { "DepartmentID" });
DropIndex("dbo.RecommendedBook", new[] { "CourseID" });
DropTable("dbo.RecommendedBook");
}
}
When your migration fails you are given a couple of options:
'Introducing FOREIGN KEY constraint 'FK_dbo.RecommendedBook_dbo.Department_DepartmentID' on table 'RecommendedBook' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.
Could not create constraint or index. See previous errors.'
Here is an example of using the 'modify other FOREIGN KEY constraints' by setting 'cascadeDelete' to false in the migration file and then run 'update-database'.

Make your Foreign key attributes nullable. That will work.

This sounds weird and I don't know why, but in my case that was happening because my ConnectionString was using "." in "data source" attribute. Once I changed it to "localhost" it workded like a charm. No other change was needed.

The existing answers are great I just wanted to add that I ran into this error because of a different reason. I wanted to create an Initial EF migration on an existing DB but I didn't use the -IgnoreChanges flag and applied the Update-Database command on an empty Database (also on the existing fails).
Instead I had to run this command when the current db structure is the current one:
Add-Migration Initial -IgnoreChanges
There is likely a real problem in the db structure but save the world one step at a time...

In .NET 5 < and .NET Core 2.0 < you can use .OnDelete(DeleteBehavior.Restrict) in OnModelCreating like #Nexus23 answer but you do not need to disable cascade for every model.
Example with join entity type configuration many-to-many:
internal class MyContext : DbContext
{
public MyContext(DbContextOptions<MyContext> options)
: base(options)
{
}
public DbSet<Post> Posts { get; set; }
public DbSet<Tag> Tags { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Post>()
.HasMany(p => p.Tags)
.WithMany(p => p.Posts)
.UsingEntity<PostTag>(
j => j
.HasOne(pt => pt.Tag)
.WithMany(t => t.PostTags)
.HasForeignKey(pt => pt.TagId)
.OnDelete(DeleteBehavior.Restrict),
j => j
.HasOne(pt => pt.Post)
.WithMany(p => p.PostTags)
.HasForeignKey(pt => pt.PostId)
.OnDelete(DeleteBehavior.Restrict),
j =>
{
j.Property(pt => pt.PublicationDate).HasDefaultValueSql("CURRENT_TIMESTAMP");
j.HasKey(t => new { t.PostId, t.TagId });
});
}
}
public class Post
{
public int PostId { get; set; }
public string Title { get; set; }
public string Content { get; set; }
public ICollection<Tag> Tags { get; set; }
public List<PostTag> PostTags { get; set; }
}
public class Tag
{
public string TagId { get; set; }
public ICollection<Post> Posts { get; set; }
public List<PostTag> PostTags { get; set; }
}
public class PostTag
{
public DateTime PublicationDate { get; set; }
public int PostId { get; set; }
public Post Post { get; set; }
public string TagId { get; set; }
public Tag Tag { get; set; }
}
Sources:
https://learn.microsoft.com/en-us/ef/core/modeling/relationships?tabs=fluent-api%2Cfluent-api-simple-key%2Csimple-key#join-entity-type-configuration
https://learn.microsoft.com/en-us/dotnet/api/microsoft.entityframeworkcore.deletebehavior?view=efcore-5.0
This does require you to remove the many to many relationship yourself or you will receive the following error when you remove a parent entity:
The association between entity types '' and '' has been severed, but
the relationship is either marked as required or is implicitly
required because the foreign key is not nullable. If the
dependent/child entity should be deleted when a required relationship
is severed, configure the relationship to use cascade deletes.
Consider using 'DbContextOptionsBuilder.EnableSensitiveDataLogging' to
see the key values
You can solve this by using DeleteBehavior.ClientCascade instead which will allow EF to perform cascade deletes on loaded entities.
internal class MyContext : DbContext
{
public MyContext(DbContextOptions<MyContext> options)
: base(options)
{
}
public DbSet<Post> Posts { get; set; }
public DbSet<Tag> Tags { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Post>()
.HasMany(p => p.Tags)
.WithMany(p => p.Posts)
.UsingEntity<PostTag>(
j => j
.HasOne(pt => pt.Tag)
.WithMany(t => t.PostTags)
.HasForeignKey(pt => pt.TagId)
.OnDelete(DeleteBehavior.Cascade),
j => j
.HasOne(pt => pt.Post)
.WithMany(p => p.PostTags)
.HasForeignKey(pt => pt.PostId)
.OnDelete(DeleteBehavior.ClientCascade),
j =>
{
j.Property(pt => pt.PublicationDate).HasDefaultValueSql("CURRENT_TIMESTAMP");
j.HasKey(t => new { t.PostId, t.TagId });
});
}
}
public class Post
{
public int PostId { get; set; }
public string Title { get; set; }
public string Content { get; set; }
public ICollection<Tag> Tags { get; set; }
public List<PostTag> PostTags { get; set; }
}
public class Tag
{
public string TagId { get; set; }
public ICollection<Post> Posts { get; set; }
public List<PostTag> PostTags { get; set; }
}
public class PostTag
{
public DateTime PublicationDate { get; set; }
public int PostId { get; set; }
public Post Post { get; set; }
public string TagId { get; set; }
public Tag Tag { get; set; }
}
https://learn.microsoft.com/en-us/dotnet/api/microsoft.entityframeworkcore.deletebehavior?view=efcore-5.0

None of the aforementioned solutions worked for me. What I had to do was use a nullable int (int?) on the foreign key that was not required (or not a not null column key) and then delete some of my migrations.
Start by deleting the migrations, then try the nullable int.
Problem was both a modification and model design. No code change was necessary.

The simple way is to, Edit your migration file (cascadeDelete: true) into (cascadeDelete: false) then after assign the Update-Database command in your Package Manager Console.if it's problem with your last migration then all right. Otherwise check your earlier migration history, copy those things, paste into your last migration file, after that do it the same thing. it perfectly works for me.

You could add this in your DataContext.cs, this works for me...
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
modelBuilder.Conventions.Remove<ManyToManyCascadeDeleteConvention>();
}

I ran into the same problem and stuck for a long. The following steps saved me.
Go through the constraints and change the onDelete ReferentialAction to NoAction from Cascade
constraints: table =>
{
table.PrimaryKey("PK_table1", x => x.Id);
table.ForeignKey(
name: "FK_table1_table2_table2Id",
column: x => x.table2Id,
principalTable: "table2",
principalColumn: "Id",
onDelete: ReferentialAction.NoAction);
});

Problem with seeding my many-many EF relationships in Code First Database [duplicate]

I've been wrestling with this for a while and can't quite figure out what's happening. I have a Card entity which contains Sides (usually 2) - and both Cards and Sides have a Stage. I'm using EF Codefirst migrations and the migrations are failing with this error:
Introducing FOREIGN KEY constraint 'FK_dbo.Sides_dbo.Cards_CardId' on
table 'Sides' may cause cycles or multiple cascade paths. Specify ON
DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY
constraints.
Here's my Card entity:
public class Card
{
public Card()
{
Sides = new Collection<Side>();
Stage = Stage.ONE;
}
[Key]
[Required]
public virtual int CardId { get; set; }
[Required]
public virtual Stage Stage { get; set; }
[Required]
[ForeignKey("CardId")]
public virtual ICollection<Side> Sides { get; set; }
}
Here's my Side entity:
public class Side
{
public Side()
{
Stage = Stage.ONE;
}
[Key]
[Required]
public virtual int SideId { get; set; }
[Required]
public virtual Stage Stage { get; set; }
[Required]
public int CardId { get; set; }
[ForeignKey("CardId")]
public virtual Card Card { get; set; }
}
And here's my Stage entity:
public class Stage
{
// Zero
public static readonly Stage ONE = new Stage(new TimeSpan(0, 0, 0), "ONE");
// Ten seconds
public static readonly Stage TWO = new Stage(new TimeSpan(0, 0, 10), "TWO");
public static IEnumerable<Stage> Values
{
get
{
yield return ONE;
yield return TWO;
}
}
public int StageId { get; set; }
private readonly TimeSpan span;
public string Title { get; set; }
Stage(TimeSpan span, string title)
{
this.span = span;
this.Title = title;
}
public TimeSpan Span { get { return span; } }
}
What's odd is that if I add the following to my Stage class:
public int? SideId { get; set; }
[ForeignKey("SideId")]
public virtual Side Side { get; set; }
The migration runs successfully. If I open up SSMS and look at the tables, I can see that Stage_StageId has been added to Cards (as expected/desired), however Sides contains no reference to Stage (not expected).
If I then add
[Required]
[ForeignKey("StageId")]
public virtual Stage Stage { get; set; }
public int StageId { get; set; }
To my Side class, I see StageId column added to my Side table.
This is working, but now throughout my application, any reference to Stage contains a SideId, which is in some cases totally irrelevant. I'd like to just give my Card and Side entities a Stage property based on the above Stage class without polluting the stage class with reference properties if possible... what am I doing wrong?

Because Stage is required, all one-to-many relationships where Stage is involved will have cascading delete enabled by default. It means, if you delete a Stage entity
the delete will cascade directly to Side
the delete will cascade directly to Card and because Card and Side have a required one-to-many relationship with cascading delete enabled by default again it will then cascade from Card to Side
So, you have two cascading delete paths from Stage to Side - which causes the exception.
You must either make the Stage optional in at least one of the entities (i.e. remove the [Required] attribute from the Stage properties) or disable cascading delete with Fluent API (not possible with data annotations):
modelBuilder.Entity<Card>()
.HasRequired(c => c.Stage)
.WithMany()
.WillCascadeOnDelete(false);
modelBuilder.Entity<Side>()
.HasRequired(s => s.Stage)
.WithMany()
.WillCascadeOnDelete(false);

I had a table that had a circular relationship with others and I was getting the same error. Turns out it is about the foreign key which was not nullable. If the key is not nullable the related object must be deleted, and circular relations don't allow that. So use nullable foreign key.
[ForeignKey("StageId")]
public virtual Stage Stage { get; set; }
public int? StageId { get; set; }

Anybody wondering how to do it in EF core:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
foreach (var relationship in modelBuilder.Model.GetEntityTypes().SelectMany(e => e.GetForeignKeys()))
{
relationship.DeleteBehavior = DeleteBehavior.Restrict;
}
..... rest of the code.....

I was getting this error for lots of entities when I was migrating down from an EF7 model to an EF6 version. I didn't want to have to go through each entity one at a time, so I used:
builder.Conventions.Remove<ManyToManyCascadeDeleteConvention>();
builder.Conventions.Remove<OneToManyCascadeDeleteConvention>();

You can set cascadeDelete to false or true (in your migration Up() method). Depends upon your requirement.
AddForeignKey("dbo.Stories", "StatusId", "dbo.Status", "StatusID", cascadeDelete: false);

In .NET Core I changed the onDelete option to ReferencialAction.NoAction
constraints: table =>
{
table.PrimaryKey("PK_Schedule", x => x.Id);
table.ForeignKey(
name: "FK_Schedule_Teams_HomeId",
column: x => x.HomeId,
principalTable: "Teams",
principalColumn: "Id",
onDelete: ReferentialAction.NoAction);
table.ForeignKey(
name: "FK_Schedule_Teams_VisitorId",
column: x => x.VisitorId,
principalTable: "Teams",
principalColumn: "Id",
onDelete: ReferentialAction.NoAction);
});

I had this issue also, I solved it instantly with this answer from a similar thread
In my case, I didn't want to delete the dependent record on key deletion. If this is the case in your situation just simply change the Boolean value in the migration to false:
AddForeignKey("dbo.Stories", "StatusId", "dbo.Status", "StatusID", cascadeDelete: false);
Chances are, if you are creating relationships which throw this compiler error but DO want to maintain cascade delete; you have an issue with your relationships.

I fixed this. When you add the migration, in the Up() method there will be a line like this:
.ForeignKey("dbo.Members", t => t.MemberId, cascadeDelete:True)
If you just delete the cascadeDelete from the end it will work.

Just for documentation purpose, to someone that comes on the future, this thing can be solved as simple as this, and with this method, you could do a method that disabled one time, and you could access your method normally
Add this method to the context database class:
protected override void OnModelCreating(DbModelBuilder modelBuilder) {
modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
}

In .NET Core I played with all upper answers - but without any success.
I made changes a lot in DB structure and every time added new migration attempting to update-database, but received the same error.
Then I started to remove-migration one by one until Package Manager Console threw me exception:
The migration '20170827183131_***' has already been applied to the database
After that, I added new migration (add-migration) and update-database successfully
So my suggestion would be: clear out all your temp migrations, until your current DB state.

public partial class recommended_books : DbMigration
{
public override void Up()
{
CreateTable(
"dbo.RecommendedBook",
c => new
{
RecommendedBookID = c.Int(nullable: false, identity: true),
CourseID = c.Int(nullable: false),
DepartmentID = c.Int(nullable: false),
Title = c.String(),
Author = c.String(),
PublicationDate = c.DateTime(nullable: false),
})
.PrimaryKey(t => t.RecommendedBookID)
.ForeignKey("dbo.Course", t => t.CourseID, cascadeDelete: false) // was true on migration
.ForeignKey("dbo.Department", t => t.DepartmentID, cascadeDelete: false) // was true on migration
.Index(t => t.CourseID)
.Index(t => t.DepartmentID);
}
public override void Down()
{
DropForeignKey("dbo.RecommendedBook", "DepartmentID", "dbo.Department");
DropForeignKey("dbo.RecommendedBook", "CourseID", "dbo.Course");
DropIndex("dbo.RecommendedBook", new[] { "DepartmentID" });
DropIndex("dbo.RecommendedBook", new[] { "CourseID" });
DropTable("dbo.RecommendedBook");
}
}
When your migration fails you are given a couple of options:
'Introducing FOREIGN KEY constraint 'FK_dbo.RecommendedBook_dbo.Department_DepartmentID' on table 'RecommendedBook' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.
Could not create constraint or index. See previous errors.'
Here is an example of using the 'modify other FOREIGN KEY constraints' by setting 'cascadeDelete' to false in the migration file and then run 'update-database'.

Make your Foreign key attributes nullable. That will work.

This sounds weird and I don't know why, but in my case that was happening because my ConnectionString was using "." in "data source" attribute. Once I changed it to "localhost" it workded like a charm. No other change was needed.

The existing answers are great I just wanted to add that I ran into this error because of a different reason. I wanted to create an Initial EF migration on an existing DB but I didn't use the -IgnoreChanges flag and applied the Update-Database command on an empty Database (also on the existing fails).
Instead I had to run this command when the current db structure is the current one:
Add-Migration Initial -IgnoreChanges
There is likely a real problem in the db structure but save the world one step at a time...

In .NET 5 < and .NET Core 2.0 < you can use .OnDelete(DeleteBehavior.Restrict) in OnModelCreating like #Nexus23 answer but you do not need to disable cascade for every model.
Example with join entity type configuration many-to-many:
internal class MyContext : DbContext
{
public MyContext(DbContextOptions<MyContext> options)
: base(options)
{
}
public DbSet<Post> Posts { get; set; }
public DbSet<Tag> Tags { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Post>()
.HasMany(p => p.Tags)
.WithMany(p => p.Posts)
.UsingEntity<PostTag>(
j => j
.HasOne(pt => pt.Tag)
.WithMany(t => t.PostTags)
.HasForeignKey(pt => pt.TagId)
.OnDelete(DeleteBehavior.Restrict),
j => j
.HasOne(pt => pt.Post)
.WithMany(p => p.PostTags)
.HasForeignKey(pt => pt.PostId)
.OnDelete(DeleteBehavior.Restrict),
j =>
{
j.Property(pt => pt.PublicationDate).HasDefaultValueSql("CURRENT_TIMESTAMP");
j.HasKey(t => new { t.PostId, t.TagId });
});
}
}
public class Post
{
public int PostId { get; set; }
public string Title { get; set; }
public string Content { get; set; }
public ICollection<Tag> Tags { get; set; }
public List<PostTag> PostTags { get; set; }
}
public class Tag
{
public string TagId { get; set; }
public ICollection<Post> Posts { get; set; }
public List<PostTag> PostTags { get; set; }
}
public class PostTag
{
public DateTime PublicationDate { get; set; }
public int PostId { get; set; }
public Post Post { get; set; }
public string TagId { get; set; }
public Tag Tag { get; set; }
}
Sources:
https://learn.microsoft.com/en-us/ef/core/modeling/relationships?tabs=fluent-api%2Cfluent-api-simple-key%2Csimple-key#join-entity-type-configuration
https://learn.microsoft.com/en-us/dotnet/api/microsoft.entityframeworkcore.deletebehavior?view=efcore-5.0
This does require you to remove the many to many relationship yourself or you will receive the following error when you remove a parent entity:
The association between entity types '' and '' has been severed, but
the relationship is either marked as required or is implicitly
required because the foreign key is not nullable. If the
dependent/child entity should be deleted when a required relationship
is severed, configure the relationship to use cascade deletes.
Consider using 'DbContextOptionsBuilder.EnableSensitiveDataLogging' to
see the key values
You can solve this by using DeleteBehavior.ClientCascade instead which will allow EF to perform cascade deletes on loaded entities.
internal class MyContext : DbContext
{
public MyContext(DbContextOptions<MyContext> options)
: base(options)
{
}
public DbSet<Post> Posts { get; set; }
public DbSet<Tag> Tags { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Post>()
.HasMany(p => p.Tags)
.WithMany(p => p.Posts)
.UsingEntity<PostTag>(
j => j
.HasOne(pt => pt.Tag)
.WithMany(t => t.PostTags)
.HasForeignKey(pt => pt.TagId)
.OnDelete(DeleteBehavior.Cascade),
j => j
.HasOne(pt => pt.Post)
.WithMany(p => p.PostTags)
.HasForeignKey(pt => pt.PostId)
.OnDelete(DeleteBehavior.ClientCascade),
j =>
{
j.Property(pt => pt.PublicationDate).HasDefaultValueSql("CURRENT_TIMESTAMP");
j.HasKey(t => new { t.PostId, t.TagId });
});
}
}
public class Post
{
public int PostId { get; set; }
public string Title { get; set; }
public string Content { get; set; }
public ICollection<Tag> Tags { get; set; }
public List<PostTag> PostTags { get; set; }
}
public class Tag
{
public string TagId { get; set; }
public ICollection<Post> Posts { get; set; }
public List<PostTag> PostTags { get; set; }
}
public class PostTag
{
public DateTime PublicationDate { get; set; }
public int PostId { get; set; }
public Post Post { get; set; }
public string TagId { get; set; }
public Tag Tag { get; set; }
}
https://learn.microsoft.com/en-us/dotnet/api/microsoft.entityframeworkcore.deletebehavior?view=efcore-5.0

None of the aforementioned solutions worked for me. What I had to do was use a nullable int (int?) on the foreign key that was not required (or not a not null column key) and then delete some of my migrations.
Start by deleting the migrations, then try the nullable int.
Problem was both a modification and model design. No code change was necessary.

The simple way is to, Edit your migration file (cascadeDelete: true) into (cascadeDelete: false) then after assign the Update-Database command in your Package Manager Console.if it's problem with your last migration then all right. Otherwise check your earlier migration history, copy those things, paste into your last migration file, after that do it the same thing. it perfectly works for me.

You could add this in your DataContext.cs, this works for me...
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
modelBuilder.Conventions.Remove<ManyToManyCascadeDeleteConvention>();
}

I ran into the same problem and stuck for a long. The following steps saved me.
Go through the constraints and change the onDelete ReferentialAction to NoAction from Cascade
constraints: table =>
{
table.PrimaryKey("PK_table1", x => x.Id);
table.ForeignKey(
name: "FK_table1_table2_table2Id",
column: x => x.table2Id,
principalTable: "table2",
principalColumn: "Id",
onDelete: ReferentialAction.NoAction);
});

Introducing FOREIGN KEY constraint may cause cycles or multiple cascade [duplicate]

I've been wrestling with this for a while and can't quite figure out what's happening. I have a Card entity which contains Sides (usually 2) - and both Cards and Sides have a Stage. I'm using EF Codefirst migrations and the migrations are failing with this error:
Introducing FOREIGN KEY constraint 'FK_dbo.Sides_dbo.Cards_CardId' on
table 'Sides' may cause cycles or multiple cascade paths. Specify ON
DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY
constraints.
Here's my Card entity:
public class Card
{
public Card()
{
Sides = new Collection<Side>();
Stage = Stage.ONE;
}
[Key]
[Required]
public virtual int CardId { get; set; }
[Required]
public virtual Stage Stage { get; set; }
[Required]
[ForeignKey("CardId")]
public virtual ICollection<Side> Sides { get; set; }
}
Here's my Side entity:
public class Side
{
public Side()
{
Stage = Stage.ONE;
}
[Key]
[Required]
public virtual int SideId { get; set; }
[Required]
public virtual Stage Stage { get; set; }
[Required]
public int CardId { get; set; }
[ForeignKey("CardId")]
public virtual Card Card { get; set; }
}
And here's my Stage entity:
public class Stage
{
// Zero
public static readonly Stage ONE = new Stage(new TimeSpan(0, 0, 0), "ONE");
// Ten seconds
public static readonly Stage TWO = new Stage(new TimeSpan(0, 0, 10), "TWO");
public static IEnumerable<Stage> Values
{
get
{
yield return ONE;
yield return TWO;
}
}
public int StageId { get; set; }
private readonly TimeSpan span;
public string Title { get; set; }
Stage(TimeSpan span, string title)
{
this.span = span;
this.Title = title;
}
public TimeSpan Span { get { return span; } }
}
What's odd is that if I add the following to my Stage class:
public int? SideId { get; set; }
[ForeignKey("SideId")]
public virtual Side Side { get; set; }
The migration runs successfully. If I open up SSMS and look at the tables, I can see that Stage_StageId has been added to Cards (as expected/desired), however Sides contains no reference to Stage (not expected).
If I then add
[Required]
[ForeignKey("StageId")]
public virtual Stage Stage { get; set; }
public int StageId { get; set; }
To my Side class, I see StageId column added to my Side table.
This is working, but now throughout my application, any reference to Stage contains a SideId, which is in some cases totally irrelevant. I'd like to just give my Card and Side entities a Stage property based on the above Stage class without polluting the stage class with reference properties if possible... what am I doing wrong?

Because Stage is required, all one-to-many relationships where Stage is involved will have cascading delete enabled by default. It means, if you delete a Stage entity
the delete will cascade directly to Side
the delete will cascade directly to Card and because Card and Side have a required one-to-many relationship with cascading delete enabled by default again it will then cascade from Card to Side
So, you have two cascading delete paths from Stage to Side - which causes the exception.
You must either make the Stage optional in at least one of the entities (i.e. remove the [Required] attribute from the Stage properties) or disable cascading delete with Fluent API (not possible with data annotations):
modelBuilder.Entity<Card>()
.HasRequired(c => c.Stage)
.WithMany()
.WillCascadeOnDelete(false);
modelBuilder.Entity<Side>()
.HasRequired(s => s.Stage)
.WithMany()
.WillCascadeOnDelete(false);

I had a table that had a circular relationship with others and I was getting the same error. Turns out it is about the foreign key which was not nullable. If the key is not nullable the related object must be deleted, and circular relations don't allow that. So use nullable foreign key.
[ForeignKey("StageId")]
public virtual Stage Stage { get; set; }
public int? StageId { get; set; }

Anybody wondering how to do it in EF core:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
foreach (var relationship in modelBuilder.Model.GetEntityTypes().SelectMany(e => e.GetForeignKeys()))
{
relationship.DeleteBehavior = DeleteBehavior.Restrict;
}
..... rest of the code.....

I was getting this error for lots of entities when I was migrating down from an EF7 model to an EF6 version. I didn't want to have to go through each entity one at a time, so I used:
builder.Conventions.Remove<ManyToManyCascadeDeleteConvention>();
builder.Conventions.Remove<OneToManyCascadeDeleteConvention>();

You can set cascadeDelete to false or true (in your migration Up() method). Depends upon your requirement.
AddForeignKey("dbo.Stories", "StatusId", "dbo.Status", "StatusID", cascadeDelete: false);

In .NET Core I changed the onDelete option to ReferencialAction.NoAction
constraints: table =>
{
table.PrimaryKey("PK_Schedule", x => x.Id);
table.ForeignKey(
name: "FK_Schedule_Teams_HomeId",
column: x => x.HomeId,
principalTable: "Teams",
principalColumn: "Id",
onDelete: ReferentialAction.NoAction);
table.ForeignKey(
name: "FK_Schedule_Teams_VisitorId",
column: x => x.VisitorId,
principalTable: "Teams",
principalColumn: "Id",
onDelete: ReferentialAction.NoAction);
});

I had this issue also, I solved it instantly with this answer from a similar thread
In my case, I didn't want to delete the dependent record on key deletion. If this is the case in your situation just simply change the Boolean value in the migration to false:
AddForeignKey("dbo.Stories", "StatusId", "dbo.Status", "StatusID", cascadeDelete: false);
Chances are, if you are creating relationships which throw this compiler error but DO want to maintain cascade delete; you have an issue with your relationships.

I fixed this. When you add the migration, in the Up() method there will be a line like this:
.ForeignKey("dbo.Members", t => t.MemberId, cascadeDelete:True)
If you just delete the cascadeDelete from the end it will work.

Just for documentation purpose, to someone that comes on the future, this thing can be solved as simple as this, and with this method, you could do a method that disabled one time, and you could access your method normally
Add this method to the context database class:
protected override void OnModelCreating(DbModelBuilder modelBuilder) {
modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
}

In .NET Core I played with all upper answers - but without any success.
I made changes a lot in DB structure and every time added new migration attempting to update-database, but received the same error.
Then I started to remove-migration one by one until Package Manager Console threw me exception:
The migration '20170827183131_***' has already been applied to the database
After that, I added new migration (add-migration) and update-database successfully
So my suggestion would be: clear out all your temp migrations, until your current DB state.

public partial class recommended_books : DbMigration
{
public override void Up()
{
CreateTable(
"dbo.RecommendedBook",
c => new
{
RecommendedBookID = c.Int(nullable: false, identity: true),
CourseID = c.Int(nullable: false),
DepartmentID = c.Int(nullable: false),
Title = c.String(),
Author = c.String(),
PublicationDate = c.DateTime(nullable: false),
})
.PrimaryKey(t => t.RecommendedBookID)
.ForeignKey("dbo.Course", t => t.CourseID, cascadeDelete: false) // was true on migration
.ForeignKey("dbo.Department", t => t.DepartmentID, cascadeDelete: false) // was true on migration
.Index(t => t.CourseID)
.Index(t => t.DepartmentID);
}
public override void Down()
{
DropForeignKey("dbo.RecommendedBook", "DepartmentID", "dbo.Department");
DropForeignKey("dbo.RecommendedBook", "CourseID", "dbo.Course");
DropIndex("dbo.RecommendedBook", new[] { "DepartmentID" });
DropIndex("dbo.RecommendedBook", new[] { "CourseID" });
DropTable("dbo.RecommendedBook");
}
}
When your migration fails you are given a couple of options:
'Introducing FOREIGN KEY constraint 'FK_dbo.RecommendedBook_dbo.Department_DepartmentID' on table 'RecommendedBook' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.
Could not create constraint or index. See previous errors.'
Here is an example of using the 'modify other FOREIGN KEY constraints' by setting 'cascadeDelete' to false in the migration file and then run 'update-database'.

Make your Foreign key attributes nullable. That will work.

This sounds weird and I don't know why, but in my case that was happening because my ConnectionString was using "." in "data source" attribute. Once I changed it to "localhost" it workded like a charm. No other change was needed.

The existing answers are great I just wanted to add that I ran into this error because of a different reason. I wanted to create an Initial EF migration on an existing DB but I didn't use the -IgnoreChanges flag and applied the Update-Database command on an empty Database (also on the existing fails).
Instead I had to run this command when the current db structure is the current one:
Add-Migration Initial -IgnoreChanges
There is likely a real problem in the db structure but save the world one step at a time...

In .NET 5 < and .NET Core 2.0 < you can use .OnDelete(DeleteBehavior.Restrict) in OnModelCreating like #Nexus23 answer but you do not need to disable cascade for every model.
Example with join entity type configuration many-to-many:
internal class MyContext : DbContext
{
public MyContext(DbContextOptions<MyContext> options)
: base(options)
{
}
public DbSet<Post> Posts { get; set; }
public DbSet<Tag> Tags { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Post>()
.HasMany(p => p.Tags)
.WithMany(p => p.Posts)
.UsingEntity<PostTag>(
j => j
.HasOne(pt => pt.Tag)
.WithMany(t => t.PostTags)
.HasForeignKey(pt => pt.TagId)
.OnDelete(DeleteBehavior.Restrict),
j => j
.HasOne(pt => pt.Post)
.WithMany(p => p.PostTags)
.HasForeignKey(pt => pt.PostId)
.OnDelete(DeleteBehavior.Restrict),
j =>
{
j.Property(pt => pt.PublicationDate).HasDefaultValueSql("CURRENT_TIMESTAMP");
j.HasKey(t => new { t.PostId, t.TagId });
});
}
}
public class Post
{
public int PostId { get; set; }
public string Title { get; set; }
public string Content { get; set; }
public ICollection<Tag> Tags { get; set; }
public List<PostTag> PostTags { get; set; }
}
public class Tag
{
public string TagId { get; set; }
public ICollection<Post> Posts { get; set; }
public List<PostTag> PostTags { get; set; }
}
public class PostTag
{
public DateTime PublicationDate { get; set; }
public int PostId { get; set; }
public Post Post { get; set; }
public string TagId { get; set; }
public Tag Tag { get; set; }
}
Sources:
https://learn.microsoft.com/en-us/ef/core/modeling/relationships?tabs=fluent-api%2Cfluent-api-simple-key%2Csimple-key#join-entity-type-configuration
https://learn.microsoft.com/en-us/dotnet/api/microsoft.entityframeworkcore.deletebehavior?view=efcore-5.0
This does require you to remove the many to many relationship yourself or you will receive the following error when you remove a parent entity:
The association between entity types '' and '' has been severed, but
the relationship is either marked as required or is implicitly
required because the foreign key is not nullable. If the
dependent/child entity should be deleted when a required relationship
is severed, configure the relationship to use cascade deletes.
Consider using 'DbContextOptionsBuilder.EnableSensitiveDataLogging' to
see the key values
You can solve this by using DeleteBehavior.ClientCascade instead which will allow EF to perform cascade deletes on loaded entities.
internal class MyContext : DbContext
{
public MyContext(DbContextOptions<MyContext> options)
: base(options)
{
}
public DbSet<Post> Posts { get; set; }
public DbSet<Tag> Tags { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<Post>()
.HasMany(p => p.Tags)
.WithMany(p => p.Posts)
.UsingEntity<PostTag>(
j => j
.HasOne(pt => pt.Tag)
.WithMany(t => t.PostTags)
.HasForeignKey(pt => pt.TagId)
.OnDelete(DeleteBehavior.Cascade),
j => j
.HasOne(pt => pt.Post)
.WithMany(p => p.PostTags)
.HasForeignKey(pt => pt.PostId)
.OnDelete(DeleteBehavior.ClientCascade),
j =>
{
j.Property(pt => pt.PublicationDate).HasDefaultValueSql("CURRENT_TIMESTAMP");
j.HasKey(t => new { t.PostId, t.TagId });
});
}
}
public class Post
{
public int PostId { get; set; }
public string Title { get; set; }
public string Content { get; set; }
public ICollection<Tag> Tags { get; set; }
public List<PostTag> PostTags { get; set; }
}
public class Tag
{
public string TagId { get; set; }
public ICollection<Post> Posts { get; set; }
public List<PostTag> PostTags { get; set; }
}
public class PostTag
{
public DateTime PublicationDate { get; set; }
public int PostId { get; set; }
public Post Post { get; set; }
public string TagId { get; set; }
public Tag Tag { get; set; }
}
https://learn.microsoft.com/en-us/dotnet/api/microsoft.entityframeworkcore.deletebehavior?view=efcore-5.0

None of the aforementioned solutions worked for me. What I had to do was use a nullable int (int?) on the foreign key that was not required (or not a not null column key) and then delete some of my migrations.
Start by deleting the migrations, then try the nullable int.
Problem was both a modification and model design. No code change was necessary.

The simple way is to, Edit your migration file (cascadeDelete: true) into (cascadeDelete: false) then after assign the Update-Database command in your Package Manager Console.if it's problem with your last migration then all right. Otherwise check your earlier migration history, copy those things, paste into your last migration file, after that do it the same thing. it perfectly works for me.

You could add this in your DataContext.cs, this works for me...
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
modelBuilder.Conventions.Remove<ManyToManyCascadeDeleteConvention>();
}

I ran into the same problem and stuck for a long. The following steps saved me.
Go through the constraints and change the onDelete ReferentialAction to NoAction from Cascade
constraints: table =>
{
table.PrimaryKey("PK_table1", x => x.Id);
table.ForeignKey(
name: "FK_table1_table2_table2Id",
column: x => x.table2Id,
principalTable: "table2",
principalColumn: "Id",
onDelete: ReferentialAction.NoAction);
});

Entity Framework Many to Many - Cannot get data

I have introduced a many to many relationship between two of my existing tables. For this, I have added a third table, which contains only the Ids of the other two tables.
Since I am using EF, I have also added
public virtual List<EntityOne> EntityOnes in EntityTwo
and
public virtual List<EntityTwo> EntityTwos in EntityOne.
However, with this, when I get the EntityTwo object, it does not contain the associated EntityOne object. The list has a count of zero, even though the data is there in the tables.
Am I missing something here? Is there anything else, I need to do?
Not sure,if this is relevant, but I have also this in OnModelCreation
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<EntityOne>().
HasMany(p => p.EntityTwos).
WithMany(a => a.EntityOnes).
Map(
m =>
{
m.MapLeftKey("EntityTwoId");
m.MapRightKey("EntityOneId");
m.ToTable("EntityRelations");
});
////Make sure a context is not created by default.
}

Try this:
public partial class One
{
[Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public virtual int Id { get; set; }
private ICollection<OneTwo> _oneTwos;
public virtual ICollection<OneTwo> OneTwos
{
get { return _oneTwos ?? (_oneTwos = new List<OneTwo>()); }
set { _oneTwos = value; }
}
}
public partial class Two
{
[Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public virtual int Id { get; set; }
private ICollection<OneTwo> _oneTwos;
public virtual ICollection<OneTwo> OneTwos
{
get { return _oneTwos ?? (_oneTwos = new List<OneTwo>()); }
set { _oneTwos = value; }
}
}
Add navigation properties to the join class:
public partial class OneTwo
{
public virtual int OneId { get; set; }
public virtual int TwoId { get; set; }
public virtual One One { get; set; }
public virtual Two Two { get; set; }
}
Add composite key to the join class and configure relationships:
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<OneTwo>() // composite primary key
.HasKey(p => new { p.OneId, p.TwoId });
modelBuilder.Entity<OneTwo>()
.HasRequired(a => a.One)
.WithMany(c => c.OneTwos)
.HasForeignKey(fk => fk.OneId)
.WillCascadeOnDelete(false);
modelBuilder.Entity<OneTwo>()
.HasRequired(a => a.Two)
.WithMany(c => c.OneTwos)
.HasForeignKey(fk => fk.TwoId)
.WillCascadeOnDelete(false);
// TODO: handle orphans when last asociation is deleted
}
An alternative strategy is to configure EF relationships via EntityTypeConfiguration<>. The following many-to-many relationship implementation demonstrates that approach:
City.cs
public partial class City
{
public virtual int Id { get; set; }
private ICollection<CountyCity> _countiesCities;
public virtual ICollection<CountyCity> CountiesCities
{
get { return _countiesCities ?? (_countiesCities = new List<CountyCity>()); }
set { _countiesCities = value; }
}
}
County.cs
public partial class County
{
public virtual int Id { get; set; }
private ICollection<CountyCity> _countiesCities;
public virtual ICollection<CountyCity> CountiesCities
{
get { return _countiesCities ?? (_countiesCities = new List<CountyCity>()); }
set { _countiesCities = value; }
}
}
CountyCity.cs
public partial class CountyCity
{
public virtual int CountyId { get; set; }
public virtual int CityId { get; set; }
public virtual County County { get; set; }
public virtual City City { get; set; }
}
CountyCityConfiguration.cs (EF 6 implementation)
public class CountyCityConfiguration : IEntityTypeConfiguration<CountyCity>
{
public void Map(EntityTypeBuilder<CountyCity> builder)
{
// Table and Schema Name declarations are optional
//ToTable("CountyCity", "dbo");
// composite primary key
builder.HasKey(p => new { p.CountyId, p.CityId });
builder.HasOne(pt => pt.County)
.WithMany(p => p.CountiesCities)
.HasForeignKey(pt => pt.CountyId)
.OnDelete(DeleteBehavior.Restrict);
builder.HasOne(pt => pt.City)
.WithMany(t => t.CountiesCities)
.HasForeignKey(pt => pt.CityId)
.OnDelete(DeleteBehavior.Restrict);
// TODO: handle orphans when last association is deleted
}
}
Entity Framework 6 Implementations:
You may configure the composite key and relationships using EntityTypeConfiguration<> as the previous code demonstrates.
Entity Framework Core Implementations:
EntityTypeConfiguration<> has not yet been migrated. However, it is on the roadmap for the next release.
In the meantime, you can employ the temporary pattern suggested by the EF team, or one of the patterns discussed this rather lengthy StackOverflow post discussing entity configuration in Entity Framework 7.
I implemented the pattern posted by Cocowalla in the lengthy discussion prior to reading the EF Team post. The source code for my workaround is available in this GitHub repository.
IEntityTypeConfiguration.cs
namespace Dna.NetCore.Core.DAL.EFCore.Configuration.Temporary.Cocowalla
{
// attribute: https://stackoverflow.com/questions/26957519/ef-7-mapping-entitytypeconfiguration/35373237#35373237
public interface IEntityTypeConfiguration<TEntityType> where TEntityType : class
{
void Map(EntityTypeBuilder<TEntityType> builder);
}
}
Here is my implementation of that pattern:
namespace Dna.NetCore.Core.DAL.EFCore.Configuration.Common
{
public class StateOrProvinceConfiguration : IEntityTypeConfiguration<StateOrProvince>
{
public void Map(EntityTypeBuilder<StateOrProvince> builder)
{
// EF Core
builder.HasOne(p => p.Country).WithMany(p => p.StateOrProvinces).HasForeignKey(s => s.CountryId).OnDelete(DeleteBehavior.Cascade);
builder.HasMany(d => d.Cities).WithOne().OnDelete(DeleteBehavior.Cascade);
builder.HasMany(d => d.Counties).WithOne().OnDelete(DeleteBehavior.Cascade);
}
}
}

How to define EF Many To Many Relationship in type that has other relationships to the same other type

This is quite a simple problem that has quite a long explanation so please bear with me if this gets long. (i'm really going to try and keep it to a minimum)
Ok so here's my "extracted sample" that produces the same problem ...
public class TestContext : DbContext
{
public DbSet<TypeA> TypeAs { get; set; }
public DbSet<TypeB> TypeBees { get; set; }
}
public class TypeA
{
[Key]
public int Id { get; set; }
public int SpecialBId { get; set; }
public virtual ICollection<TypeB> Bees { get; set; }
public virtual TypeB SpecialB { get; set; }
}
public class TypeB
{
[Key]
public int Id { get; set; }
public virtual ICollection<TypeA> Aaas { get; set; }
}
... so I enable EF Migrations, run add migration, run update database and I get this ...
What I would expect to see is a join table for the many to many, but for some reason that second "SpecialB" reference causes this to break the many to many reference / redefine it somehow.
So I figured uh ok ... maybe it just needs a hand so I added an onmodel create to my context ...
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<TypeA>().HasMany<TypeB>(i => i.Bees);
modelBuilder.Entity<TypeB>().HasMany<TypeA>(i => i.Aaas);
}
Generation of a migration at this point produces nothing.
So, how do I get these relationships to work
correctly and produce the correct db structure?
Just in case ...
This is what Ef generates when running add-migration to create an initial migration for the db context above with the types as defined:
public partial class Initial : DbMigration
{
public override void Up()
{
CreateTable(
"dbo.TypeAs",
c => new
{
Id = c.Int(nullable: false, identity: true),
SpecialBId = c.Int(nullable: false),
})
.PrimaryKey(t => t.Id)
.ForeignKey("dbo.TypeBs", t => t.SpecialBId, cascadeDelete: true)
.Index(t => t.SpecialBId);
CreateTable(
"dbo.TypeBs",
c => new
{
Id = c.Int(nullable: false, identity: true),
TypeA_Id = c.Int(),
})
.PrimaryKey(t => t.Id)
.ForeignKey("dbo.TypeAs", t => t.TypeA_Id)
.Index(t => t.TypeA_Id);
}
public override void Down()
{
DropForeignKey("dbo.TypeAs", "SpecialBId", "dbo.TypeBs");
DropForeignKey("dbo.TypeBs", "TypeA_Id", "dbo.TypeAs");
DropIndex("dbo.TypeBs", new[] { "TypeA_Id" });
DropIndex("dbo.TypeAs", new[] { "SpecialBId" });
DropTable("dbo.TypeBs");
DropTable("dbo.TypeAs");
}
}

You need to add WithMany():
modelBuilder.Entity<TypeA>().HasMany<TypeB>(i => i.Bees).WithMany();
modelBuilder.Entity<TypeB>().HasMany<TypeA>(i => i.Aaas).WithMany();

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