LINQ 查询对父元素和子元素进行分组

Question

我目前正在开发一个 .NET 4.7 应用程序。我需要用未排序的数据创建一个树结构。

最终的树形结构如下所示：

public class LocationViewModel
{
    public int Id { get; set; }
    public string Code { get; set; }
    public List<LocationViewModel> ChildLocations { get; set; }
}

一个父 LocationViewModel 可以有多个 ChildLocation。每个 ChildLocation 本身又可以有多个 ChildLocation。

我需要从以下结构中对数据进行排序。我的未排序数据是List<LinkParentChildViewModel> LinksParentChild，如下所示：

public class LinkParentChildViewModel
{
    public Location Parent { get; set; }
    public LocationLink Child { get; set; }
}

public class Location
{
   public int Id { get; set; }
   public string Code { get; set; }
}

public class LocationLink
{
   public int ParentLocationId { get; set; }
   public int ChildLocationId { get; set; }
}

首先我有一个List<Location> Locations，其中包含所有位置。

然后我得到一个List<LinkParentChildViewModel> LinksParentChild，所有条目都混淆了——因此父母可以是孩子，孩子可以是父母。

var LinksParentChild = new List<LinkParentChildViewModel>
{
    new LinkParentChildViewModel
    {
        Parent = new Location
        {
            Id = 8,
            Code = "ParLoc1",
        },
        Child = new LocationLink
        {
            ChildLocationId = 4,
            ParentLocationId = null
        }
    },
    new LinkParentChildViewModel
    {
        Parent = new Location
        {
            Id = 4,
            Code = "Loc1",
        },
        Child = new LocationLink
        {
            ChildLocationId = 6,
            ParentLocationId = 8
        }
    },
    new LinkParentChildViewModel
    {
        Parent = new Location
        {
            Id = 6,
            Code = "ChildLoc1",
        },
        Child = new LocationLink
        {
            ChildLocationId = null,
            ParentLocationId = 4
        }
    },
    new LinkParentChildViewModel
    {
        Parent = new Location
        {
            Id = 10,
            Code = "LeftLoc1",
        },
        Child = new LocationLink
        {
            ChildLocationId = 11,
            ParentLocationId = 4
        }
    },
    new LinkParentChildViewModel
    {
        Parent = new Location
        {
            Id = 11,
            Code = "LeftChildLoc1",
        },
        Child = new LocationLink
        {
            ChildLocationId = null,
            ParentLocationId = 10
        }
    }
};

我需要编写一个 LINQ 查询来将我数据中的所有节点分组到 List<LocationViewModel> result。

var result = LinksParentChild.GroupBy(x => x.Parent.Id).Select(x => new LocationViewModel
{
    Id = x.First().Parent.Id,
    Code = x.First().Parent.Code,
    ChildLocations = new List<LocationViewModel>
    {
        // ... I'm stuck unfortunately, somehow i need to query and group all locations
    }
}).ToList();

我试过了，但不幸的是我卡住了：

• 我需要像树状结构一样选择所有位置

你知道如何解决这个问题吗？

非常感谢！

结果如下：

var result = new List<LocationViewModel>
{
    new LocationViewModel
    {
        Id = 8,
        Code = "ParLoc1",
        ChildLocations = new List<LocationViewModel>
        {
            new LocationViewModel
            {
                Id = 4,
                Code = "Loc1",
                ChildLocations = new List<LocationViewModel>
                {
                    new LocationViewModel
                    {
                        Id = 6,
                        Code = "ChildLoc1"
                    },
                    new LocationViewModel
                    {
                        Id = 10,
                        Code = "LeftLoc1",
                        ChildLocations = new List<LocationViewModel>
                        {
                            new LocationViewModel
                            {
                                Id = 11,
                                Code = "LeftChildLoc1"
                            }
                        }
                    }
                }
            }
        }
    }
};

Answer 1

你可以试试递归

public static List<LocationViewModel> GetHierarchy(List<LinkParentChildViewModel> linkParentChildViewModels, int parentId)
{
    return linkParentChildViewModels.Where(x => x.Parent.Id == parentId).Select(x => new LocationViewModel
    {
        Id = x.Parent.Id,
        Code = x.Parent.Code,
        ChildLocations = GetHierarchy(linkParentChildViewModels, x.Child.ChildLocationId)
    }).ToList();
}

从 Main 方法调用它

var result = GetHierarchy(LinksParentChild, 8);