Linq 选择新的动态多部分列表<>

Question

我正在处理以下查询：

public void FindAllRelatedProdsByParentCat(CategoryService categoryService, string parentCatName, bool isDeleted)
{
    List<Category> allCats = categoryService.FindAll(isDeleted).ToList();

    var results = (from a in allCats.Where(x => x.Name == parentCatName)
                   join b in allCats 
                   on a.CategoryId equals b.Parentcategory into children
                   select new 
                         { 
                           ParentId = a.CategoryId, 
                           ChildrenIds = children.Select(z => z.CategoryId) 
                         }).ToList();
}

理想情况下，我想要将 select new 语句展平为 Id 对象的通用类型列表。目前我必须用两个属性组成一个匿名对象来获得我想要的东西。有人可以帮我将其重构为一个平面列表吗？这可行吗？

更新：类别实体是什么样的：

public class Category : EntityBase
{
    public Category()
    {
        Products = new List<Product>();
    }

    public Guid CategoryId { get; set; }
    public string Name { get; set; }
    public Guid? Parentcategory { get; set; }
    public bool IsDeleted { get; set; }
    public Guid OrgId { get; set; }
    public virtual List<Product> Products { get; set; }
    public virtual Organization Organization { get; set; }
}

Answer 1

我不知道我是否明白你想要什么，但是

var results = (from a in allCats.Where(x => x.Name == parentCatName)
               join b in allCats on a.CategoryId equals b.Parentcategory into children
               select new[] { a.CategoryId }.Concat(children.Select(z => z.CategoryId)))
              .SelectMany(x => x)
              .ToList();

我已经在 Entity Framework 6.1.3 上对其进行了测试，它正确地为select 行生成了一个UNION ALL...然后为CROSS APPLY 使用CROSS APPLY 来生成SelectMany (???)