How to create migrations with multiple projects architecture in ASP.NET Core 8

Question

I have created two projects in ASP.NET Core 8:

1. Web API project which contains

• Connection string in appsettings.json
• DbContext registration along with connection string in Program.cs file

2. Class library project which contains:

• Models
• Context, registered in program.cs file in Web API project
• All Entity Framework Core packages - Tools, Design, SqlServer

I have set these two projects as start in startupConfiguration. Web API project have a reference to the class library project.

And I'm running the add-migration mgnName command in the class library project.

I get an error:

Unable to create a 'DbContext' of type ''. The exception 'The configuration file 'appsettings.json' was not found and is not optional. The expected physical path was 'K:.NET CORe\FinalWebProject\FinalWebProject.Data\appsettings.json'.' was thrown while attempting to create an instance. For the different patterns supported at design time, see https://go.microsoft.com/fwlink/?linkid=851728

I have also done the design-time Db Creation but the error won't go away.

Please help me if anyone can!

Answer 1

Update from OP:

I just wanted to not use any database related package in my API project for sake of isolation, but after some research I found the solution : which is to create a DbContextFactory for Creating Migrations. And the solution I was seeking is impossible, but there is workaround which is to create the factory for creating the instance of the dbcontext.

========================

I didn't reproduce your issue in my side. Please kindly compare your codes with mine and have a try.

Firstly, I created a new .net 8 web api project in my VS, and just like what you mentioned. I added connection string in appsettings.json.

"ConnectionStrings": {
  "DefaultConnection": "xx"
},

And added DbContext registion in Program.cs

var connectionString = builder.Configuration.GetConnectionString("DefaultConnection");
builder.Services.AddDbContext<ApplicationDbContext>(options =>
    options.UseSqlServer(connectionString));

What you didn't mentioned in your question is about the nuget packages. Here's what I added in my web api project.

<ItemGroup>
  <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="8.0.8" />
  <PackageReference Include="Swashbuckle.AspNetCore" Version="6.4.0" />
 <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="8.0.8">
  <PrivateAssets>all</PrivateAssets>
  <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
 </PackageReference>
</ItemGroup>

Then I created the ClassLibrary project. In this project, I created Data folder and Models folder. And my ApplicationDbContext is like below.

namespace ClassLibrary1.Data
{
    public class ApplicationDbContext : IdentityDbContext
    {
        public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
            : base(options)
        {
        }

        public DbSet<MovieRelease> MovieRel { get; set; }

    }
}

This is my Model

namespace ClassLibrary1.Models
{
    public class MovieRelease
    {
        [Key]
        public int ReleaseId { get; set; }
        public int ReleaseName { get; set; }
    }
}

And it requires nuget packages:

<ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.Identity.EntityFrameworkCore" Version="8.0.8" />
    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="8.0.8" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="8.0.8" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="8.0.8">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
    </PackageReference>
  </ItemGroup>

This is my project structure and my test result.