C#•15mo ago

✅ Layered architecture EF Core error when creating migrations

I have a Web Api project which is using .NET Core 7, my layers are DAL, Services Entities and API. I recently moved connection string to appsettings.json file (it was hardcoded in my appdbcondext class before) and created a extension method in DAL layer which sets connection string, I am using this in my startup project (API) program.cs but when I run dotnet ef migrations add testMig it gives an error

Unable to create an object of type 'ApplicationDbContext'. For the different patterns supported at design time, see https://go.microsoft.com/fwlink/?linkid=851728

Unable to create an object of type 'ApplicationDbContext'. For the different patterns supported at design time, see https://go.microsoft.com/fwlink/?linkid=851728

It was not happening when I hard code connection string in DAL layer and add/update migrations, ApplicationDbContext.cs (DAL)

namespace MeetingAppDemo.DAL.Context
{
    public class ApplicationDbContext : DbContext
    {
        public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options) : base(options)
        {
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
        }
        public DbSet<User> Users { get; set; }
        public DbSet<Meeting> Meetings { get; set; }
        public DbSet<MeetingParticipant> MeetingParticipants { get; set; }
        public DbSet<MeetingDocument> MeetingDocuments { get; set; }
    }
}

namespace MeetingAppDemo.DAL.Context
{
    public class ApplicationDbContext : DbContext
    {
        public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options) : base(options)
        {
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
        }
        public DbSet<User> Users { get; set; }
        public DbSet<Meeting> Meetings { get; set; }
        public DbSet<MeetingParticipant> MeetingParticipants { get; set; }
        public DbSet<MeetingDocument> MeetingDocuments { get; set; }
    }
}

DataAccessExtension.cs (DAL)

namespace MeetingAppDemo.DAL.Extensions
{
    public static class DataAccessExtensions
    {
        public static IServiceCollection SetupDbContext(this IServiceCollection services, string connectionString)
        {
            services.AddDbContext<ApplicationDbContext>(options =>
                options.UseSqlServer(connectionString));
            return services;
        }
    }
}

namespace MeetingAppDemo.DAL.Extensions
{
    public static class DataAccessExtensions
    {
        public static IServiceCollection SetupDbContext(this IServiceCollection services, string connectionString)
        {
            services.AddDbContext<ApplicationDbContext>(options =>
                options.UseSqlServer(connectionString));
            return services;
        }
    }
}

Program.cs (API Layer)

// Database Configuration
var dbConnectionString = builder.Configuration.GetConnectionString("Development");
builder.Services.SetupDbContext(dbConnectionString);

// Database Configuration
var dbConnectionString = builder.Configuration.GetConnectionString("Development");
builder.Services.SetupDbContext(dbConnectionString);

6 Replies

Tvde1•15mo ago

when you run dotnet ef migrations ... you need to specify the EF project and the startup project. Usually:

dotnet ef migrations add MyMigration -s MyApplication.API -p MyApplication.Data

dotnet ef migrations add MyMigration -s MyApplication.API -p MyApplication.Data

seppOP•15mo ago

I have tried that but I get different error which says

Your startup project 'MeetingAppDemo.API' doesn't reference Microsoft.EntityFrameworkCore.Design. This package is required for the Entity Framework Core Tools to work. Ensure your startup project is correct, install the package, and try again.

Your startup project 'MeetingAppDemo.API' doesn't reference Microsoft.EntityFrameworkCore.Design. This package is required for the Entity Framework Core Tools to work. Ensure your startup project is correct, install the package, and try again.

I tried installing EFCore and Design in my API project but nothing changes

Tvde1•15mo ago

yea the API needs the EFCore Design packages. Can you share the csproj file of your API?

seppOP•15mo ago

Oddly after restarting the Visual Studio add migration worked Another question, is it okay to have ef core packages installed both dal and api layer?

Tvde1•15mo ago

yeah it's necessary unfortunately

seppOP•15mo ago

Oh alright then, I assume problem solved for now. Thanks for helping 😅

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✅ Layered architecture EF Core error when creating migrations