在 EF Core 3 中映射 json

Question

City has list of stores and parks. I want to save store object as json in sql server.

public class City{
    public int Id { get; set; }
    ... 
    public ICollection<Store> Stores { get; set; }
    public ICollection<Park> Parks { get; set; }

    public City{
        Stores = new List<Store>();
        Parks = new List<Park>();
    }
}

public class Store{
    public int Id { get; set; }
    public string Name { get; set; }
}

public class Park{
    public int Id { get; set; }
    public int CityId { get; set; }
    public string Name { get; set; }
}

public class CityConfiguration : IEntityTypeConfiguration<City>
{
    public void Configure(EntityTypeBuilder<City> builder)
    {
        builder.ToTable("Cities");
        builder.HasKey(x => x.Id);

        builder.Property(e => e.Stores).HasConversion(
            v => JsonConvert.SerializeObject(v, new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore }),
            v => JsonConvert.DeserializeObject<IList<Store>>(v, new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore }));

        builder.HasMany(e => e.Parks)
            .WithOne(x => x.City)
            .HasForeignKey(f => f.CityId);
    }
}

When seeding data on test db context I'm populating Store object like this

modelBuilder.Entity<Park>(s =>
{
    s.HasData(new Park{ Name = "Park name", CityId = 1, Id = 1 });
});    

modelBuilder.Entity<Store>(s =>
{
    s.HasData(new Store{ Name = "Store name", Id = 1 });
});

When retriving data

var res = _db.Cities.Where(x => x.Id == id)
                .Include(x => x.Parks)  // this works fine           
                .Include(x => x.Stores) // this issues exception
                .FirstOrDefault();

System.InvalidOperationException: Lambda expression used inside Include is not valid.

I'm using .net core 3.1.3

Answer 1

Since you're saving the City.Stores collection as a JSON serialized string, you cannot use it as a navigation collection to child objects. You need to get rid of the .Include(x => x.Stores) in the query statement:

var res = _db.Cities.Where(x => x.Id == id)
                .Include(x => x.Parks)  // this works fine           
                .FirstOrDefault();