EF Core - How to retrieve base class and conditionally include property on derived class [duplicate]

Below is my model that captures the scenario of base class and derived class

Model

public class Group
{
    List<Item> Items { get; set; }
}

public abstract class Item 
{
    public string Name { get; set; }
}

public class ItemWithResource : Item
{
    public Resource Resource { get; set; }
}

public class ItemWithoutResource : Item
{
}

public class Resource
{
    public decimal Price { get; set; }
}

• A Group has Items
• Each Item could be an ItemWithResource or an ItemWithoutResource

I want to retrieve all items, regardless of derived type, and also include the Resource for items that are ItemWithResource

return await _context.Groups
    .Include(g => g.Items)
    // NEXT LINE WILL NOT WORK AS BASE CLASS ITEM DOES NOT HAVE PROPERTY 'Resource'
    .ThenInclude(i => i.Resource)
    .SingleOrDefaultAsync();

The code snippet above illustrates the problem. How do I write a query to 'include' Resource for Items that are an ItemWithResource?

Solution 1:

try:

...
.ThenInclude( i => ( i as ItemWithResource ).Resource )
...