Migrations Different Assembly - entity-framework

Question

I have the following structure.
MyOrg.Api (AspNet Core Web App)
MoOrg.DataAccess (Containing the DbContext)
I want the Migrations live in the DataAccess Assembly.
Ive tried almost every combination of configuration but cant get it work probably.
MyOrg.Api (Startup.cs)
public void ConfigureServices(IServiceCollection services)
{
// default stuff..
services.AddDbContext<MyOrg.DataAccess.MyDatabaseContext>(options =>
{
options.UseSqlite("Filename=./myDbContext.db", b => b.MigrationsAssembly("MyOrg.DataAccess"));
});
}
MyOrg.DataAccess
public class MyDatabaseContext : DbContext
{
public DbSet<Something> Somethings { get; set; }
public MyDatabaseContext(DbContextOptions<MyDatabaseContext> options) : base(options)
{
}
}
How to do it right?

Answer 1

In your MyOrg.DataAccess, create a new class MigrationDbContext deriving from MyDatabaseContext with and OnConfiguring method override :
public class MigrationDbContext: MyDatabaseContext
{
public MigrationDbContext()
{
}
protected override void OnConfiguring(DbContextOptionsBuilder options)
{
options.UseSqlite("Filename=./myDbContext.db");
base.OnConfiguring(options);
}
}
Since .Net Core 2.1 you don't need to add a reference to Microsoft.EntityFrameworkCore.Tools, dotnet ef is a global tool.
If you use .Net Core 2.0 or above, add the Microsoft.EntityFrameworkCore.Tools.DotNet as a DotNetCliToolReference to your MyOrg.DataAccess project :
<ItemGroup>
<DotNetCliToolReference Include="Microsoft.EntityFrameworkCore.Tools.DotNet"
Version="1.1.6" />
</ItemGroup>
Then go to your MyOrg.DataAccess project directory using a command prompt and run :
dotnet ef --startup-project ../MyOrg.Api/ migrations add Initial -c MigationDbContext
to create an initial migration named Initial (I assume ../MyOrg.Api/ is the relative path to your startup project)
To update your database run:
dotnet ef --startup-project ../MyOrg.Api/ database update
For more information read the doc Entity Framework Core tools reference - .NET CLI

Answer 2

I've managed to get it working as follows (whilst also adhering to Onion Architecture):
Create a class library 'App.Core'
Add a 'Country' domain model to this library:
public class Country
{
public int Id { get; set; }
public string Name { get; set; }
}
This is just a simple class to get things working quickly
Create a class library 'App.Infrastructure'
Add a DbContext to this library:
public class AppDbContext : DbContext
{
public DbSet<Country> Countries { get; set; }
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.UseSqlServer(#"Server=localhost;Database=App;Trusted_Connection=True;",
x => x.MigrationsAssembly("App.Migrations"));
}
}
'App.Migrations' will be our separate class library just for migrations
'App.Infrastructure' needs to reference 'Microsoft.EntityFrameworkCore.SqlServer' and 'Microsoft.EntityFrameworkCore.Tools'
Run dotnet ef migrations add InitialCreate
Do this from the command line in the 'App.Infrastructure' directory
This will create a 'Migrations' folder in your 'App.Infrastructure' class library with a migration called 'InitialCreate'
Create a class library 'App.Migrations'
Move the 'Migrations' folder from 'App.Infrastructure' to 'App.Migrations' - you will need to update the namespaces after the move
Add a project reference in 'App.Migrations' to 'App.Infrastructure'
Edit the .csproj file for 'App.Migrations' and add an output path:
netcoreapp2.1
App.Infrastructure\bin\$(Configuration)\
The above path will be correct if 'App.Infrastructure' and 'App.Migrations' are in the same directory, if not, the output path will need to be adjusted
On build this results in 'App.Migrations' being output to the 'App.Infrastructure' bin directory - we need to do this as we can't reference 'App.Migrations' in 'App.Infrastructure' as this results in a circular reference, so this is a workaround
Build the solution
Run dotnet ef database update from the command line in the 'App.Infrastructure' directory and this should create the database and create the 'Countries' table
Run dotnet ef migrations add AddCity --project App.Migrations for your next migration
'AddCity' is just another migration to create a 'Cities' table - this requires adding a 'City' class and updating the DbContext
Run the command from the 'App.Infrastructure' directory and the migration will be added to the 'App.Migrations' class library
Remember to rebuild the solution every time a migration is added