In my project, for some reason i have two separate repositories (with different DbContext and schema). Now, i need to create a foreign key from one model class inDbContextB to another model class in DbContextA, assuming that DbContextA is already applied to database.
//This is a code snippet in DbContextB.IEntityTypeConfiguration<ModelClassB>() method.
builder
.HasOne(col => col.PropertyA)
.WithOne()
.HasForeignKey<ModelClassB>(col => col.PropertyAId)
.IsRequired();
The problem is, DbContextB will automatically create a table for ModelClassA while this table is already existed, because i run DbContextA migration script first.
However, One way to achieve this is to manually insert the foreign key into generated migration script (ModelClassB.PropertyAId is enough for me and i don't care about its navigation property ModelClassB.PropertyA).
The question is: How can i force DbContextB to add a foreign key without need to add its corresponding table?
For EF Core < 5.0, the general approach for this scenario has been to use a special context only for migrations, that contains all model classes and relationships. Your app would not use this special context.
From Ability to exclude/skip/ignore parts of the model from migrations so that a table is not created (for overlapping bounded contexts)
#2725 on GitHub:
I just found a workaround
Create another DbContext that inherit your DbContext, for example MigrationDbContext. Override the OnModelCreating method and ingore entities that you want it's table not being generated.
protected override void OnModelCreating(ModelBuilder builder)
{
base.OnModelCreating(builder);
builder.Ignore<Category>();
}
Create another class that implement IDbContextFactory. For example
public class MigrationContextFactory : IDbContextFactory<MigrationDbContext>
{
public MigrationDbContext Create()
{
var optionsBuilder = new DbContextOptionsBuilder<MigrationDbContext>();
optionsBuilder.UseSqlite("Data Source=blog.db");
return new MigrationDbContext(optionsBuilder.Options);
}
}
The migration tool will discover this MigrationContextFactory and use the MigrationDbContext.
For EF Core >= 5.0, version 5.0.0-rc1 introduces the brand new Relational:IsTableExcludedFromMigrations annotation, that you can set e.g. by using the new entity.ToTable(string name, bool excludedFromMigrations) Fluent API extension method overload.
I'm a bit stuck trying to add a shadow propery to my existing entities. I add shadow property in OnModelCreating. The property is configured like this:
public override void Configure(EntityTypeBuilder<TEntity> builder)
{
builder.Property<Guid>("TenantId")
.HasDefaultValue(CommonConstants.DefaultTenantId);
base.Configure(builder);
}
Then I run add-migration and get this error:
The seed entity for entity type SomeEntity cannot be added because there was no value provided for the required property TenantId.
Although the value has been provided as you see above.
My expectation was that migration would determine the changes, add new column TenantId and populate existing entries in the database with the default value.
Any ideas how to make it work?
UPD: A have already read this issue, which confirms my assumption that migration should pick up the default value.
There are similar questions with this issue, but not for EF Core. Not a duplicate of Entity Framework Core Using multiple DbContexts . That one is related to not being able to access the database at all from the second context, and the two contexts use different databases. This question is about a single database and the issue is related to migrations
I have two EF core db contexts using the same SQL Server database.
In the first context I have many entities, one of them is User.
In the second one there is a single entity called UserExt which has a navigational property to User
public class UserExt
{
[Key]
public long UserID { get; set; }
public virtual User User { get; set; }
[Required]
public string Address { get; set; }
}
The issue is that when creating the migration for UserExt using 'add-migration', all entities from the first context are also included.
Tried providing the context, but same result
add-migration --context SecondContext
With EF 6 it was possible to solve this using ContextKey (https://msdn.microsoft.com/en-us/library/system.data.entity.migrations.dbmigrationsconfiguration.contextkey(v=vs.113).aspx) but has not been ported to EF Core
Is there a way to make this work so that the migrations in the second context would contain only its entities ?
Solved using database context inheritance. This way I can have separate migrations.
public class SecondDbContext : FirstDbContext
{
public virtual DbSet<UserExt> ExtendedUsers { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.UseSqlServer("connectionString", options =>
options
.MigrationsAssembly("SecondDbContextAssemblyName")
.MigrationsHistoryTable("__SecondEFMigrationsHistory") // separate table to store migration history to avoid conflicts
);
}
}
Because SecondDbContext is inherited from FirstDbContext, every entity change made in the base context will be inherited. Which means that when a new migration is added to the second context, it will try to apply the changes again from the first context again. Workaround is to:
Add a new migration (for example Add-Migration Inherit_FirstDbContext)
Delete everything from the migration's Up and Down methods
Apply the empty migration in the database. (Update-Database)
This ensures that the Entity Framework snapshot will contain the changes, without actually having to re-apply them in the database.
look at this question for example.
Entity Framework (EF) Code First Cascade Delete for One-to-Zero-or-One relationship
I have a normal context etc.
If i change anything, i can generate a new migration per Add-Migration test.
But if i change WillCascadeOnDelete() from true to false or adding some with true it is ignored by entity framework.
I'm using Code first with a generated model from database.
In the generated model everything was on WillCascadeOnDelete(false).
So now I'm changing it from false to true but its ignored by entity framework.
I tried this: http://msdn.microsoft.com/en-us/data/jj591620.aspx#CascadeDelete too.
After adding this lines ... Nothing changes if i add Add-Migration newTest.
modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>()
modelBuilder.Conventions.Remove<ManyToManyCascadeDeleteConvention>()
This is ignored, too, by Add-Migration thirdTest.
modelBuilder.Conventions.Add<OneToManyCascadeDeleteConvention>()
modelBuilder.Conventions.Add<ManyToManyCascadeDeleteConvention>()
I can change everything with WillCascadeOnDelete... It is ignored!
If i change everything else, it works and would be appended in new Migrations...
The main class for this construct is the following.
[Table("SomeToThing")]
public class SomeToThing : Base
{
[Column("Some")]
public Guid SomeId { get; set; }
[ForeignKey("SomeId")]
public virtual Some Some { get; set; }
[Column("Thing")]
public Guid ThingId { get; set; }
[ForeignKey("ThingId")]
public virtual Thing Thing { get; set; }
}
I have this tables:
Some
SomeToThing
Thing
The SomeToThing has additional variables and because that i can't map Some directly to Thing.
I know this thread is old, but I was just having the same issue.
My solution was to delete the migration source file and re-scaffolding it from scratch.
On my first try I forgot to set .WillCascadeOnDelete(false), and for good reasons, SQL Server rejected the migration due to cycles. Then when I tried to re-scaffold the migration using the same name after removing cascades in the OnModelCreating method, EF just wouldn't pick up those particular changes.
Then I deleted the migration source file and ran Add-Migration SameMigrationName. Cascade deletes were removed, and seems like it worked, since MSSQL accepted the migration script. I'm using EF 6.1.3 btw.
One thing I would like to mention, relating to the problem I was having, was that I added the following code (to my 'OnModelCreating', ie DbContext):
modelBuilder.Entity<MyEntityTwo>()
.HasMany(e => e.MyEntityOne)
.WithRequired(e => e.MyEntityTwo)
.HasForeignKey(e => e.MyEntityTwoId)
.WillCascadeOnDelete(false);
but I added this AFTER the table defining MyEntityOne was already defined, ie in a previous migration.
Turns out that since I added this to OnModelCreating after the table was already defined, entity framework did 'not' pickup the willcascadeondelete(false) when I added a new migration.
To fix this, I had to manually add the following to (new) migration:
DropIndex(...this was created by EF for me already. Not important...);
DropForeignKey("MyEntityOne", "<name of Foreign key goes here ie FK_MyEntityOne_...etc>");
AddForeignKey("MyEntityOne", "MyEntityTwoId", "MyEntityTwo", "Id", cascadeDelete:false);
AlterColumn(...this was created by EF for me already. Not important...);
CreateIndex(...this was created by EF for me already. Not important...);
By adding the AddForeignKey line, with cascadeDelete: false, it will re-apply the foreign key with cacade on delete false this time.
I have a local database that is currently in it's second version and should now go to it's third version.
The code for the previous migrations was generated by another programmer so I am assuming I am doing something wrong here.
In my model there are around 30 classes, and inside the model folder there is a mapping folder and it contains the mappings for those 30 classes.
So now I added 1 new class in the same manner as those previous classes and then run the add-migration command in the Package Manager Console.
Infortunately I get an empty migration Up() and Down() method.
When I look in the database there is a __migrationHistory available with the previous 2 migrations. If I run my application now, the third migration is also added but obviously the new table is not being created because it's not in the Up() method.
What could I be doing wrong?
I think something is going wrong when scaffolding the previous migrations... It's like it can't find the new Code-First classes I have added.
This is my command:
add-migration "1.2" -verbose -ProjectName "MyEFproject"
I am assuming that the scaffolding doesn't know where to look for the new class... or is this by convention that all model classes are just expected to be in the project?
Result of add-migration:
namespace MyProject.Migrations
{
using System;
using System.Data.Entity.Migrations;
public partial class _1002 : DbMigration
{
public override void Up()
{
}
public override void Down()
{
}
}
}
Sample of new Model Class:
using System;
using System.Collections.Generic;
namespace MyProject.Models
{
public partial class MyTable
{
public string SomeId { get; set; }
public string SomeText { get; set; }
}
}
Sample of new Mapping class
using System.ComponentModel.DataAnnotations.Schema;
using System.Data.Entity.ModelConfiguration;
namespace MyProject.Models.Mapping
{
public class MyTableMap : EntityTypeConfiguration<MyTable>
{
public MyTableMap()
{
// Primary Key
this.HasKey(t => t.SomeId);
// Properties
this.Property(t => t.SomeText)
.IsRequired()
.HasMaxLength(30);
// Table & Column Mappings
this.ToTable("MyTable", "database");
this.Property(t => t.SomeId).HasColumnName("SomeId");
this.Property(t => t.SomeText).HasColumnName("SomeText");
}
}
}
Thank you,
You need to add your table to your implementation of the DbContext class, e.g.
public class MyDatabaseEntities : DbContext {
public virtual DbSet<MyTable> MyTable { get; set; }
}
While rolling back an existing EF Core Data Context back to empty, my migrations wouldn't generate until I removed the ApplicationDbContextModelSnapshot that accompanied the migrations.
This class is auto-generated and needs to align with your current migration level.
I was able to fix this issue by deleting a record of last migration from _MigrationHistory table.
This record had been incorrectly created before I added DbSet for new model object to DbContext class.
After this deletion new migration was created with correct Up() and Down() methods.
I had this problem because I forgot to add {get; set;} after my variable names
You need to add your table to your implementation of the DbContext class, e.g. While rolling back an existing EF Core Data Context back to empty, my migrations wouldn't generate until I REMOVED the ApplicationDbContextModelSnapshot that accompanied the migrations.
In my case, the datacontext project is a class lib project. It is different from the startup project which is asp.net mvc 5 project. Now by mistake the connection string in the startup project is pointing to a different database.
So ensure that datacontext project and startup project point to the same database. Also use the full command as mentioned in the question like the following. You can include -Force as well.
add-migration "InitialMigration" -verbose -ProjectName "MyEFproject" -Force
Also: Make sure any new properties you've added are public!
In my case I was doing a migration where I added fields to an existing table and was ending up with empty Up and Down methods,
I had something like this:
public bool ExistingField { get; set; }
bool NewField { get;set; }
Can you spot the difference...?
If you make this mistake rerun the migration with the same name (you probably will need to add the -Force parameter to scaffold it full).
PS. Always make sure your project builds fully before attempting to do any kind of EF command. If your project doesn't already build you're asking for trouble.
You need to add your MyTable in Dbset and your issue will be resolved:
public DbSet<MyTable> MyTables { get; set; }
I was getting empty migrations added when I had mistakenly related two tables using a 1-many relationship rather than a many-many (i.e. i forgot one of the navigation properties). I had a seeding file that was expecting a many-many relationship and was subsequently failing during the migration causing the migration to fail. Unfortunately there was no output that made it obvious that was the problem and it was only by using the Entity Framework Power Tools (v4 but installed in VS2015) did i visually see the incorrect relationship and realize it was probably the cause.
I had to Update-Database with the latest migration before the empty one appending this parameter -TargetMigration:"{your-migration-name}".
Probably it will tell you that there will be data loss from the next buggy one we tried. If you can afford it append -Force to it.
Then I tried to add my new Add-Migration and it wasn't empty.
Final thing that you may need to do if above is throwing exception is to go SQL Server Management Studio and delete the last Automatic migration and try to add it again.
if new tables added to Context
just remove new table in "Migration/ExampleContextModelSnapshot"
I had the same issue on EFcore. When renaming Phone -> mobile, the migration came up empty.
My DbContext :
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<MyUser>()
.Property(c => c.Mobile)
.HasColumnName("phone");
}
Problem was using .HasColumnName("phone") was overriding the actual property name so EF probably couldn't see any change.
Changing string value made it work.
I had this exact issue after I wanted to add an extra column to my database. Because my data would not seed unless the tables were empty, I deleted all the tables and the migrations to recreate the tables. When I tried to migrate, the migration had empty up and down methods.
I solved this by deleting the snapshot file as this was creating the issue. So I deleted all the migrations and the snapshot file, added the migration again and ran update database. The tables and migrations were successfully updated with my new column.
A better way to do this though is to run the down method and drop the tables like that if you are working on test data. Obviously this is bad in the real world to drop tables.
To me the problem was that Id property that should correspond to table id was named FeedbackId.
I changed to "Id" and then Up/Down weren't empty anymore.
Dunno if that can help somehow
If your project is small, i.e. you do not have too many migrations yet, you can delete all from your Migration folder. After that, add the migrations again.
I think this also happens when u try to do migration without any changes in the models. eg when you do migration one and succeed, when u try to do migration2 without doing any changes in any of the models, it will create empty UP and Down.
From the perspective of a complete Entity Framework (Core) beginner:
Create your class which will become your table
You can have subclasses with many-to-many or one-to-one relationships.
In step 3 you see the context where both properties have a one-to-one relationship.
Ensure you have one DbContext
If you have more than one DbContext you need to specify which context you want to add the migration to with the -Context parameter.
Add your class to your DbContext as shown by #CondingIntrigue
As a reference The Entity Framework Core DbSet
public class AccountContext : DbContext
{
public DbSet<Account> Accounts { get; set; }
public DbSet<SecretIdentity> SecretIdentity { get; set; }
}
Enter Add-Migration
In my case, I was encountering similar problems with Visual Studio Code.
I have fixed these by doing the following:
Check inside your ContextModelSnapshot : ModelSnapshot
Comment Model Entity Definition…
Delete your migration files related to these entity
Delete the migrations from the dbo.__EFMigrationsHistory table
Compile your solution.
Run the following commands:
dotnet ef migrations add migrationName -p ProjectContainer/
dotnet watch run
Temprorary remove
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
}
and then do initial create
Add-Migration InitialCreate
If after adding your class in the dbContext and your migration is still empty: do the following:
In your DbContextModelSnapshot class, remove every related code to that class name that you are trying to apply add-migration on. Save the DbContextModelSnapshot.cs and use the Add-Migration "Added_filename"
This work for me.
In my case ,I deleted Migration folder completely. As long as I didn't remove the "ApplicationDbContextModelSnapshot" and all previous migrationas it didn't work.
For me it was because I hadn't add Configuration files.
onModelCreating:
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.ApplyConfigurationsFromAssembly(typeof(AppDbContext).Assembly);
}
and add configurations in same assembly derived from IEntityTypeConfiguration<T> where T is your model.
I missed adding
{get;set}
After adding getter and setter, up and down methods are not empty.