DependencyResolver.cs

public class DependencyResolver
{
    public IServiceProvider ServiceProvider { get; }
    public string CurrentDirectory { get; set; }
    public Action<IServiceCollection> RegisterServices { get; }

    public DependencyResolver(Action<IServiceCollection> registerServices = null)
    {
        // Set up Dependency Injection
        var serviceCollection = new ServiceCollection();
        RegisterServices = registerServices;
        ConfigureServices(serviceCollection);
        ServiceProvider = serviceCollection.BuildServiceProvider();
    }

    private void ConfigureServices(IServiceCollection services)
    {
        // Register env and config services
        services.AddTransient<IEnvironmentService, EnvironmentService>();
        services.AddTransient<IConfigurationService, ConfigurationService>
            (provider => new ConfigurationService(provider.GetService<IEnvironmentService>())
            {
                CurrentDirectory = CurrentDirectory
            });

        // Register DbContext class
        services.AddTransient(provider =>
        {
            var configService = provider.GetService<IConfigurationService>();
            var connectionString = configService.GetConfiguration().GetConnectionString(nameof(SampleDbContext));
            var optionsBuilder = new DbContextOptionsBuilder<SampleDbContext>();
            optionsBuilder.UseSqlServer(connectionString, builder => builder.MigrationsAssembly("NetCoreLambda.EF.Design"));
            return new SampleDbContext(optionsBuilder.Options);
        });

        // Register other services
        RegisterServices?.Invoke(services);
    }
}