ProductsDbContextFactory3

ProductsDbContextFactory3.cs

public class ProductsDbContextFactory : IDesignTimeDbContextFactory<ProductsDbContext>
{
    public ProductsDbContext CreateDbContext(string[] args)
    {
        // Get environment
        string environment = Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT");

        // Build config
        IConfiguration config = new ConfigurationBuilder()
            .SetBasePath(Path.Combine(Directory.GetCurrentDirectory(), "../EfDesignDemo.Web"))
            .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
            .AddJsonFile($"appsettings.{environment}.json", optional: true)
            .AddEnvironmentVariables()
            .Build();

        // Get connection string
        var optionsBuilder = new DbContextOptionsBuilder<ProductsDbContext>();
        var connectionString = config.GetConnectionString(nameof(ProductsDbContext));
        optionsBuilder.UseSqlServer(connectionString, b => b.MigrationsAssembly("EfDesignDemo.EF.Design"));
        return new ProductsDbContext(optionsBuilder.Options);
    }
}

This code maybe will fail for migration bundle for production environment, since the EFDesifnDemo.Web folder might not exists, you can have a fallback folder to prevent the error and support ef migrations bundle

internal static class IConfigurationRootExtensions
    {
        public static IConfigurationBuilder AddBasePath(this IConfigurationBuilder builder)
        {
            var currentDirectory = Directory.GetCurrentDirectory();
            var startupProjectPath = Path.Combine(currentDirectory, "../EfDesignDemo.Web");
            var basePathConfiguration = Directory.Exists(startupProjectPath) ? startupProjectPath : currentDirectory;

            return builder.SetBasePath(basePathConfiguration);
        }
    }

And just call AddBasePath instead of setBasePath

IConfiguration config = new ConfigurationBuilder()
            .AddBasePath()