Linq投影到DTO的嵌套/分层集合

Question

I have a User and Product entities which are defined as follows:

public class User {

    Guid Id { get; set; }
    Guid ParentId { get; set; }       
    ICollection<Product> PermittedProducts { get; set; }
    ICollection<User> Children { get; set; }
}

public class Product {

    int Id { get; set; }
    string Name { get; set; }
    ICollection<User> PermittedUsers { get; set; }
}

Conceptually, a Product has a collection of PermittedUsers - ie users that can purchase the product. Additionally, each User has a collection of PermittedProducts , as well as a collection of child users, who also have their own collection of PermittedProducts .

I need to run a query via a repository to return a list of products. The repository method and DTO are defined as:

  public ICollection<ProductListDto> GetProductsForUser(Guid userId) {
       // Linq query here
  }

  public class ProductListDto {

      int Id { get; set; }
      string Name { get; set; }
      ICollection<User> Users { get; set; }
  }

The repository method needs to take a Guid userId and retrieve the PermittedProducts for that User AND the PermittedProducts for the user's children.

For example, if a product is available for a user and his two children, then the ProductListDto would have all three users in it's users collection.

As a further example, if a product is not available for a user, but it is available for his children, then this would need to be returned as well.

Both the Product and User are available as aggregate roots, so I can use either a ProductRepository or UserRepository to query through, via EntityFramework's DbSet .

At the moment my repository method is in the UserRepository (but could move to the ProductRepository if the query is simpler) and looks like:

 public ICollection<ProductListDto> GetProductsForUser(Guid userId) {
       // Linq query here - Set is the EF DbSet<User> 
       var products = from u in 
           Set.Where(x => x.Id == userId) //.... NOT SURE ABOUT THE REST!

  }

My problem is I cannot work out how to write the Linq query to achieve what I need to do!

EDIT

The answers so far don't address how to achieve the projection to the ProductListDto

Answer 1

How I would approach this is simply build a list of Id's from the parent UserId so this will contain the Parent UserId and all of it's ChildId's. From this list we can then select from Products where PermittedUsers contains one of these Id's. This is where you can get the product list from.

        var childIds = DbContext.Users.Where(x => x.Id == userId).SelectMany(y => y.Children.Select(z => z.Id)).ToList();
        childIds.Add(userId);
        var products = DbContext.Products.Where(x => x.Users.SelectMany(y => childIds.Contains(y.Id))).ToList();

Answer 2

Try this

userRepository.Where(u => u.Id == userId && u.ParentId == userId)
            .SelectMany(u => u.PermittedProducts)
            .GroupBy(p => p.Id)
            .Select(u => u.First());

Line explanation - 1) Retrieves target user and his children - 2) Select all products from user collection we get in first line - 3- 4) Remove duplicates.

Note such linq can be translated into heavy sql query that can decrease performance. Maybe it is better to call ToList after lines (1, 2 or 3). Also it is possible to write your own SQL query, store them in sql server and call them from code by name.