Infrastructure

The main purpose of this layer is to implement repository interfaces which were defined in Domain layer. If you need to customize the entity classes to fit the infrastructure (like EF) or optimize the DB, you can do it here.

It’s named {namespace}.{feature}.{infrastructure}. Eg: Juice.Abc.EF

Basically, we will create a DbContext that inherits DbContextBase to work with the database. Then use the created DbContext to implement repositories.

The project tree will look like this:

|-- Dtos    // optional
|-- Migrations   // only if you have selected a DB backend for your application 
|-- Repositories
|   |-- AbcRepository.cs   
|-- DependencyInjection     // optional
|   |-- YourServiceCollectionExtensions.cs  // to register your infrastructure services
|-- YourDbContext.cs

Separate migrations

If you want to support multiple DB backends like SqlServer, PostgreSQL… then you need to separate migrations into other projects. Eg: Juice.Abc.EF.SqlServer and Juice.Abc.EF.PostgreSQL.

These are steps to separete migrations:

  • Firstly, you must implement an IDesignTimeDbContextFactory for your DBContext
    ...
    using Juice.Extensions.DependencyInjection;
    ...

    public class AbcDbContextFactory : IDesignTimeDbContextFactory<AbcDbContext>
    {
        public WorkflowDbContext CreateDbContext(string[] args)
        {
            Environment.SetEnvironmentVariable("ASPNETCORE_ENVIRONMENT", "Development");
            var resolver = new DependencyResolver
            {
                CurrentDirectory = AppContext.BaseDirectory
            };

            resolver.ConfigureServices(services =>
            {

                // Register DbContext class
                var configService = services.BuildServiceProvider().GetRequiredService<IConfigurationService>();

                var configuration = configService.GetConfiguration(args);

                var provider = configuration.GetSection("Provider").Get<string>() ?? "SqlServer";
                var connectionName =
                    provider switch
                    {
                        "PostgreSQL" => "PostgreConnection",
                        "SqlServer" => "SqlServerConnection",
                        _ => throw new NotSupportedException($"Unsupported provider: {provider}")
                    }
                ;
                var connectionString = configuration.GetConnectionString(connectionName);

                services.AddDbContext<AbcDbContext>(options =>
                {
                    switch (provider)
                    {
                        case "PostgreSQL":
                            AppContext.SetSwitch("Npgsql.EnableLegacyTimestampBehavior", true);

                            options.UseNpgsql(
                               connectionString,
                                x =>
                                {
                                    x.MigrationsAssembly("Juice.Abc.EF.PostgreSQL");
                                });
                            break;

                        case "SqlServer":

                            options.UseSqlServer(
                                connectionString,
                                x =>
                                {
                                    x.MigrationsAssembly("Juice.Abc.EF.SqlServer");
                                });
                            break;
                        default:
                            throw new NotSupportedException($"Unsupported provider: {provider}");
                    }

                });

            });

            return resolver.ServiceProvider.GetRequiredService<AbcDbContext>();
        }
    }
  • Create a web application then add references to all infrastructure projects. Eg: Juice.Abc.Host
    • Register your DbContext into IServiceCollection
    • Set it as a startup project
  • In the Package Manager Console
    • Select the Default project to your backend project as same as the provider that you want to generate the migration. Eg: Juice.Abc.EF.PostgreSQL
    • Exec command:
Add-Migration InitDb -Context AbcDbContext -OutputDir Migrations -Args "--provider PostgreSQL"

CQRS

The typical CQRS implementation will segregate the Read/Write model and also segregate the Read/Write DB. So it can be used together with complex pattern Event Sourcing or is it simply complicated to implement for newbies.

However, a simpler approach is to use ReadOnly DB to query or read models. It’s supported by several types of databases. So you can create a DBContext intended to be read-only and use it with a read-only connection string.