EF Core 6 - TPH Querying with navigation properties

Question

I'm trying to make a poylmorphic query with different navigation properties based on the type of a TPH hierarchy.

Here is my EF Core query:

var composition = await _context.FundCompositions
            .Where(compo => compo.FundId == fundId && compo.Date == datetime)
            .Select(compo => new CompositionDto
            {
                FundId = compo.FundId,
                Date = compo.Date,
                FundName = compo.Fund.Name,
                Cash = compo.CompositionItems
                    .Where(item => item.Asset is Cash)
                    .Select(item => new CashDto
                    {
                        Id = item.AssetId,
                        Amount = item.Amount,
                        Currency = item.Asset.Currency,
                        Name = item.Asset.Name,
                        Quantity = item.Quantity,
                        Country = item.Asset.SecurityType,
                        Region = item.Asset.SecurityType,
                        GicsSector = item.Asset.SecurityType,
                        SecurityType = item.Asset.SecurityType
                    }),
                Basket = compo.CompositionItems
                    .Where(item => item.Asset is Basket)
                    .Select(item => new BasketDto
                    {
                        Id = item.AssetId,
                        Amount = item.Amount,
                        Currency = item.Asset.Currency,
                        Name = item.Asset.Name,
                        Quantity = item.Quantity,
                        Country = item.Asset.SecurityType,
                        Region = item.Asset.SecurityType,
                        GicsSector = item.Asset.SecurityType,
                        SecurityType = item.Asset.SecurityType
                    }),
                Equities = compo.CompositionItems
                    .Where(item => item.Asset is Equity)
                    .Select(item => new EquityDto
                    {
                        Id = item.AssetId,
                        Amount = item.Amount,
                        Currency = item.Asset.Currency,
                        Name = item.Asset.Name,
                        Quantity = item.Quantity,
                        Country = item.Asset.Country.Name,
                        Region = item.Asset.Country.Region.Name,
                        MarketClassification = item.Asset.Country.MarketClassification,
                        SecurityType = item.Asset.SecurityType,
                        GicsSector = ((Equity)item.Asset).GicsSector,
                        Timeserie = ((Equity)item.Asset).Timeserie
                            .Where(ts => ts.Date <= datetime && ts.Date >= datetime.AddDays(-5))
                            .OrderByDescending(ts => ts.Date)
                            .Select(ts => new TimeserieDto(ts.Date, ts.MarketCap))
                            .FirstOrDefault()
                    })
            }).FirstOrDefaultAsync(ct);

As you can see I first constrain the type of my CompositionItems in the Where clause and then Select the properties I need for each derivedType.

I feel like this is tedious, alot of code is repeated and not the correct way to deal with TPH hierarchies. Is there a better way to query derived properties?

Thanks for your help

Answer 1

Apparently, this is already the best way to do it. Good to know anyway.

Thanks for your help Svyatoslav Danyliv!