EF6 -> EFCore 3.1 Left outer Joins

Question

I'm in the process of evaluating upgrading to EFCore 3.1 from EF6 and I'm stuck on simple left outer joins. We have a substantial amount of code such as the following"

                IQueryable<SearchItemResponseDataModel> items = from item in db.Item
                                                            from e in db.Ingredient.Where(a => item.ItemId == a.ItemId).DefaultIfEmpty()
                                                            select new SearchItemResponseDataModel
                                                            {
                                                                ItemId = item.ItemId,
                                                                Name = item.Name,
                                                                IsActive = item.IsActive,
                                                                Description = item.Description,
                                                                Color = e.Color
                                                            };

Works fine in EF6; however, in EFCore, I receive the following exception:

Expression of type 'Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable1[Dal.Ingredient]' cannot be used for parameter of type 'Microsoft.EntityFrameworkCore.DbSet1[Dal.Ingredient]' of method 'System.Linq.IQueryable1[Dal.Ingredient] Where[Ingredient](Microsoft.EntityFrameworkCore.DbSet1[Dal.Ingredient], System.Linq.Expressions.Expression1[System.Func2[Dal.Ingredient,System.Boolean]])'

If I rewrite it like the following, it runs without issue:

                IQueryable<SearchItemResponseDataModel> items = from item in db.Item
                                                            join e in db.Ingredient on item.ItemId equals e.ItemId into ef
                                                            from e in ef.DefaultIfEmpty()
                                                            select new SearchItemResponseDataModel
                                                            {
                                                                ItemId = item.ItemId,
                                                                Name = item.Name,
                                                                IsActive = item.IsActive,
                                                                Description = item.Description,
                                                                Color = e.Color
                                                            };

So, it appears it's caused by the conflicted namespace between System.Linq and Microsoft.EntityFrameworkCore.

I added

public static class DbSetExtensions
{
    public static IAsyncEnumerable<TEntity> AsAsyncEnumerable<TEntity>(this Microsoft.EntityFrameworkCore.DbSet<TEntity> obj) where TEntity : class
    {
        return Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.AsAsyncEnumerable(obj);
    }

    public static IQueryable<TEntity> Where<TEntity>(this Microsoft.EntityFrameworkCore.DbSet<TEntity> obj, System.Linq.Expressions.Expression<Func<TEntity, bool>> predicate) where TEntity : class
    {
        return System.Linq.Queryable.Where(obj, predicate);
    }
}

to the base of my class per the recomendation here: https://github.com/dotnet/efcore/issues/18220

If I remove this override, this works:

IQueryable<SearchItemResponseDataModel> items = from item in db.Item.AsQueryable()
                                                        from e in db.Ingredient.AsQueryable().Where(a => item.ItemId == a.ItemId).DefaultIfEmpty()
                                                        select new SearchItemResponseDataModel
                                                        {
                                                            ItemId = item.ItemId,
                                                            Name = item.Name,
                                                            IsActive = item.IsActive,
                                                            Description = item.Description,
                                                            Color = e.Color
                                                        };

It would be great to have an override so I don't need to add .AsQueryable() everywhere :(