EntityFramework.LazyLoading

Lazy Loading for EF Core

Inspired by and partially based on the blog post: https://weblogs.asp.net/ricardoperes/implementing-missing-features-in-entity-framework-core-part-6-lazy-loading

How to enable LazyLoading in EF Core?

Enabling LazyLoading in EF Core is extremely easy with this library. You just need to call UseLazyLoading() (see step 2 below).

However, you will need to slightly modify your entity classes, but just the References, not the Collections (see step 3 below).

Step 1 - Nuget package

Reference the Microsoft.EntityFrameworkCore.LazyLoading NuGet package (https://www.nuget.org/packages/Microsoft.EntityFrameworkCore.LazyLoading/).

Step 2 - Configure the DbContext builder

Call UseLazyLoading() on the DbContextOptionsBuilder when creating the DbContext.

public class MyDbContextFactory : IDbContextFactory<MyDbContext>
{
    private readonly bool _isLazy;

    public MyDbContextFactory (bool isLazy)
    {
        _isLazy = isLazy;
    }

    public MyDbContext Create(DbContextFactoryOptions options)
    {
        var dbContextOptionsBuilder = new DbContextOptionsBuilder<MyDbContext>();
        dbContextOptionsBuilder.UseSqlServer("<some_connection_string>");

        // Here we enable LazyLoading
        dbContextOptionsBuilder.UseLazyLoading();

        return new MyDbContext(dbContextOptionsBuilder.Options);
    }
}

Step 3 - Adjust the model

In your model you need to declare References using the type LazyReference<T>. Collections don't require additional configuration in your model, just use the ICollection<> type.

public class Parent
{
    public ICollection<Child> Childs { get; set; }
}

public class Child
{
    private LazyReference<Parent> _parentLazy = new LazyReference<Parent>();
    public Parent Parent
    {
        get
        {
            return _parentLazy.GetValue(this);
        }
        set
        {
            _parentLazy.SetValue(value);
        }
    }
}

Step 4 - Done!

That's all, LazyLoading enabled! It was so easy, wasn't it?