Lazy Loading

1. In your <database>.tt file, set

   Settings.UseLazyLoading = true;

2. Make sure your connection string has ;MultipleActiveResultSets=True in it.

EF Core additional steps

• Install NuGet package: install-package Microsoft.EntityFrameworkCore.Proxies

• Include UseLazyLoadingProxies(); in your database context. For example:

  // Either in startup.cs
  public void ConfigureServices(IServiceCollection services)
  {
      services.AddDbContext<ApplicationDbContext>(options => options
          .UseSqlServer(Configuration.GetConnectionString("DefaultConnection"))
          .UseLazyLoadingProxies());
  
      ...
  }
  
  // Or in the database context
  protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
  {
      if (!optionsBuilder.IsConfigured)
      {
          optionsBuilder.UseSqlServer(@"Data Source=(local);Initial Catalog=Demo;Integrated Security=True;MultipleActiveResultSets=True;");
          optionsBuilder.UseLazyLoadingProxies();
      }
  }

Creating a website?

If you are creating a website then it's best not to use Lazy Loading as the database context is short lived (typically less than a second), can add many round-trips to the database, and you tend know up front what data you need for the view.

Prefer to .Include(p => p.Address) your related entities to load them up front in a single database call.

If you want to stay with lazy loading, that's completely fine, so long as you are aware of the extra round-trips to the database. Further reading here.