Support IReadOnlyList for Complex Collections

[tpoiesz]

What problem are you trying to solve?

It can be useful to expose collection navigation properties as IReadOnlyList to prevent client code from adding to the list directly. Instead a method is available that can do some validation and then add to the list (private property) directly. For example:

using Microsoft.EntityFrameworkCore;

const string connectionString = "Server=localhost;Database=complex-issues;Port=5432;User Id=postgres;Password=postgres;Include Error Detail=true";
var options = new DbContextOptionsBuilder<AppDbContext>()
  .UseNpgsql(connectionString)
  .Options;
var dbContext = new AppDbContext(options);
await dbContext.Database.EnsureDeletedAsync();
await dbContext.Database.EnsureCreatedAsync();

public class Entity
{
  public Guid Id { get; init; }
  private List<ComplexEntity> _complexEntities = [];
  public IReadOnlyList<ComplexEntity> ComplexEntities => _complexEntities.AsReadOnly();

  public void AddComplexEntity(ComplexEntity complexEntity)
  {
    //Some validation
    _complexEntities.Add(complexEntity);
  }
}

public class ComplexEntity
{
  public required string Value { get; init; }
}

public class AppDbContext(DbContextOptions options) : DbContext(options)
{
  public DbSet<Entity> Entities { get; init; }

  protected override void OnModelCreating(ModelBuilder modelBuilder)
  {
    base.OnModelCreating(modelBuilder);
    modelBuilder.Entity<Entity>().ComplexCollection(entity => entity.ComplexEntities).ToJson();
  }
}

This scenario is supported when using OwnsMany(...).ToJson(), but when converting to ComplexCollection we receive the following exception:

System.InvalidOperationException: The complex collection 'Entity'.'ComplexEntities' is of type 'IReadOnlyList<ComplexEntity>' which does not implement 'IList<ComplexEntity>'.

Describe the solution you'd like

For this scenario to work, so it's easier to convert from Owned entities to Complex entities

[A-Stapleton]

Any IEnumerable<T> would be nice if that possible, not sure why it was locked to a IList<T> but I am certain there was a good reason haha

[AndriySvyryd]

As long as the underlying field implements IList<T> EF could support IEnumerable<T> for the property