Add migration with different assembly c# ef-migrations entity-framework-core


I am working on a project with ASP.NET CORE 1.0.0 and I am using EntityFrameworkCore. I have separate assemblies and my project structure looks like this:

      -1 Domain
      -2 Api

In my Project.Api is the Startup class

public void ConfigureServices(IServiceCollection services)

        services.AddIdentity<IdentityUser, IdentityRole>()

The DbContext is in my Project.Data project

public class ProjectDbContext : IdentityDbContext<IdentityUser>
    public ProjectDbContext(DbContextOptions<ProjectDbContext> options) : base(options)


    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)

        var builder = new ConfigurationBuilder();
        IConfiguration Configuration = builder.Build();


When I try to make the initial migration, I get this error:

"Your target project 'Project.Api' doesn't match your migrations assembly 'Project.Data'. Either change your target project or change your migrations assembly. Change your migrations assembly by using DbContextOptionsBuilder. E.g. options.UseSqlServer(connection, b => b.MigrationsAssembly("Project.Api")). By default, the migrations assembly is the assembly containing the DbContext. Change your target project to the migrations project by using the Package Manager Console's Default project drop-down list, or by executing "dotnet ef" from the directory containing the migrations project."

After I seeing this error, I tried to execute this command located in Project.Api:

dotnet ef --startup-project ../Project.Api --assembly "../../1 Data/Project.Data" migrations add Initial

and I got this error:

"Unexpected value '../../1 Domain/Project.Data' for option 'assembly'"

I don't know why I get this error, when I try to execute the command with the '-assembly' parameter.

I can't create a Initial Migration from other assembly and I've searched for information about it but didn't got any results.

Has someone had similar issues?

4/12/2020 10:02:46 AM

Popular Answer

All EF commands have this check:

if (targetAssembly != migrationsAssembly) 
       throw MigrationsAssemblyMismatchError;

targetAssembly = the target project you are operating on. On the command line, it is the project in the current working directory. In Package Manager Console, it is whatever project is selected in the drop down box on the top right of that window pane.

migrationsAssembly = assembly containing code for migrations. This is configurable. By default, this will be the assembly containing the DbContext, in your case, Project.Data.dll. As the error message suggests, you have have a two options to resolve this

1 - Change target assembly.

cd Project.Data/
dotnet ef --startup-project ../Project.Api/ migrations add Initial

// code doesn't use .MigrationsAssembly...just rely on the default

2 - Change the migrations assembly.

cd Project.Api/
dotnet ef migrations add Initial

// change the default migrations assembly
options.UseSqlServer(connection, b => b.MigrationsAssembly("Project.Api"))
8/2/2016 5:19:18 PM

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