LINQ.Загрузка связанных элементов

Question

У меня есть сущность Contracts, ListKindWorks и KindWorks.

public partial class Contracts
{
    public Contracts()
    {
        ListKindWorks = new HashSet<ListKindWorks>();
    }

    public int Id { get; set; }
    ...
    public virtual ICollection<ListKindWorks> ListKindWorks { get; set; }
}

public partial class ListKindWorks
{
    public int IdContract { get; set; }
    public int IdKindWork { get; set; }

    public virtual Contracts IdContractNavigation { get; set; }
    public virtual KindWorks IdKindWorkNavigation { get; set; }
}

public partial class KindWorks
{
    public KindWorks()
    {
        ListKindWorks = new HashSet<ListKindWorks>();
    }

    public int Id { get; set; }
    public string Title { get; set; }
    public virtual ICollection<ListKindWorks> ListKindWorks { get; set; }
}

Я хочу загрузить связанные элементы. Примерно такой псевдокод:

source = model.Contracts
    .Select(c => new MyType
    {
        IdContract = c.Id,
        KindWork = new List<Item>
        { Id = KindWorks.Id, Value = KindWorks.Title }

        // or
        //    KindWork = c.ListKindWorks
        //           .Where(x => x.IdContract == c.Id)
        //           .Select(y => new Item 
        //           { Id = y.IdKindWork, Value = y.IdKindWorkNavigation.Title })
        ... 
    })
    .ToList();

public class Item
{
    public int Id { get; set; }
    public string Value { get; set; }
}

Могу ли я загрузить List<Item> для каждого Contracts?

Answer 1

    IEnumerable<Item> KindWork = c.ListKindWorks
    .Select(y => new Item 
    { 
        Id = y.IdKindWork, 
        Value = y.IdKindWorkNavigation.Title
    })

    IEnumerable<Item> Subject = c.ListSubjects
    .Select(y => new Item
    { 
        Id = y.IdSubject, 
        Value = y.IdSubjectNavigation.Title
    })

Answer 2

Если я понимаю, что вы ищете, я создаю Список для каждого контракта в словаре. И вот мой результат:

var contracts = new List<Contracts>
{
    new Contracts { Id = 1 },
    new Contracts { Id = 2 },
    new Contracts { Id = 3 },
};

var listKindWorks = new List<ListKindWorks>
{
    new ListKindWorks { IdContract = 1, IdKindWork = 1 },
    new ListKindWorks { IdContract = 1, IdKindWork = 2 },
    new ListKindWorks { IdContract = 2, IdKindWork = 2 },
    new ListKindWorks { IdContract = 2, IdKindWork = 3 }
};

var kindWorks = new List<KindWorks>
{
    new KindWorks { Id = 1, Title = "Title 1" },
    new KindWorks { Id = 2, Title = "Title 2" },
    new KindWorks { Id = 3, Title = "Title 3" },
};

Dictionary<Contracts, List<Item>> myDic = contracts.Select(
    contract => contract).ToDictionary(
    contract => contract,
    contract => listKindWorks.Where(
            listKindWork => listKindWork.IdContract.Equals(contract.Id))
        .Select(listKindWork => new Item
        {
            Id = kindWorks.FirstOrDefault(kindWork => kindWork.Id.Equals(listKindWork.IdKindWork))?.Id?? listKindWork.IdKindWork,
            Value = kindWorks.FirstOrDefault(kindWork => kindWork.Id.Equals(listKindWork.IdKindWork))?.Title?? "KindWork not found"
        }).ToList());

Я получаю это для моего теста:

Contract1 : Title1, Title2
Contract2 : Title2, Title3
Contract3 : Nothing