EF Core Json support with List

Is it possible to store a Json list in a DB column leveraging EF Core 7 Json support? I tried without success.

I have these classes (simplified):

public class StateData
{
    public int Id { get; set; }
    public int DemandId { get; set; }
    public List<SateItem>? MenuState { get; set; }
    public int? LastMenuItem { get; set; }
}

public class StateItem
{
    public int SideMenuItemId { get; set; }
    public int StateDataId { get; set; }
    public int Order { get; set; }
    public string Header { get; set; } = null!;
    }
}

And this DbContext:

public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
    : base(options)
{
}

public DbSet<StateData> StateData { get; set; }

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.ApplyConfiguration(new StateDataConfiguration());
}

With configuration:

public class StateDataConfiguration : IEntityTypeConfiguration<StateData>
{
    public void Configure(EntityTypeBuilder<StateData> builder)
    {
        builder.OwnsMany(d => d.MenuState, builder =>
        {
            builder.ToJson();
        });
    }
}

The goal is to store the list of StateItem's in the MenuState column as a Json array. If I just store StateItem's in a table, it works. As soon as I make them an owned class, I get this error:

> System.ArgumentException: Expression of type 'System.Object' cannot be used for assignment to type 'System.Int32'

I think, the problem has to do with primary key definition. But if I try to define primary keys, EF insists that keys need to be implicitly defined.

So, is it even possible to store Json array with EF Core's Json support?

I had the same issue, where my JSON class had an ID column. Maybe EF Core is trying to autoinsert something in to this? Worked when I removed it. Is it possible that it's interpreting your "SideMenuItemId" and "StateDataId" columns as ID columns? What if you rename them to StateDataIdentifier or something?

Maybe, using JsonProperty.EFCore can solve your problem. You can install it as a nuget package.

In your case:

using JsonProperty.EFCore;

public class StateData
{
    public int Id { get; set; }
    public int DemandId { get; set; }
    public JsonList<SateItem> MenuState { get; set; } = new();
    public int? LastMenuItem { get; set; }
}

Other usage example:

using JsonProperty.EFCore;

//Create product
var product = new Product() { Name = "Car" };

//AddRange
product.Attributes.AddRange(new Dictionary<string, object>() {
    //You can add values ​​of different types if the base type is object 
    {"MaxSpeed",300},{ "Engine capacity",3.5}, { "ElectroCar",false }
});

//Add
product.Attributes.Add("Color", "Red");

//Edit
product.Attributes.Edit(attrs=>{
    attrs["Color"] = "Blue";
    return attrs;
});

//Entity model
public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    //Json container property. Same type as JsonDictionary<string,object>
    public JsonDictionary Attributes{ get; set; } = new();
}