递归linq获得无限儿童 [英] Recursive linq to get infinite children

问题描述

我是linq的新手，我正在寻找一种方式来为父母返回父母和一个List（孩子）以及所有这些孩子。我有一个位置表，其中包含字段 LocationID ， ParentLocationID ， LOCATIONNAME 。数据样本可能如下所示：

I'm new to linq and am trying to find a way to return the parent and a List (children) and all those children, for a given parent. I have a Locations table with the fields LocationID, ParentLocationID, LocationName. A sample of the data could look like this:

ABC
 --ABC1
 --ABC2
 ----DEF1
 ----DEF2
 ----DEF3
 --ABC3
 ----DEF4
 ------GHI1
 ------GHI2
 ----DEF5
 --ABC4
 ...

如果选择的父级是ABC，那么我想返回所有的行，因为所有的子项都在它之下。但是，如果我选择父母ABC3，它将返回DEF4，GHI1，GHI2，DEF5。

Given that data, if the selected parent is 'ABC', I want to return all the rows because all children are under it. However, if I selected the parent 'ABC3', it would return DEF4, GHI1, GHI2, DEF5.

我已经研究了这些SO问题，但仍然感到困惑如何创建此语句：

I've looked into these SO questions but am still confused on how to create this statement(s):

查找自引用（parent-child）分层树中的所有后代

LINQ to SQL - 将自己加入到父级的子项（同一表）

这是我尝试过的但是出现错误：

Here's what I've tried but am getting an error:

public ActionResult Index()
{
    var loc = GetChild(346);
    return View(loc);
}

public IEnumerable<Location> GetChild(int id)
{
    DBEntities db = new DBEntities();

    var locations =  db.Locations.Where(x => x.ParentLocationID == id || x.LocationID == id).Union(
                        db.Locations.Where(x => x.ParentLocationID == id).SelectMany(y => GetChild(y.LocationID)));
    return locations;
}

而位置课程是：

public class Location
{
    public Location();

    public virtual ICollection<SimSystem> SimSystems { get; set; }
    public virtual ICollection<LocationAddress> LocationAddresses { get; set; }
    public virtual LocationType LocationType { get; set; }
    public virtual ICollection<CustomerUser> CustomerUsers { get; set; }
    public virtual ICollection<AppUserLocation> AppUserLocations { get; set; }
    public int LocationTypeID { get; set; }
    public DateTime? InstallDate { get; set; }
    public string AltPhone { get; set; }
    public string OfficePhone { get; set; }
    public int? PrimaryAddressID { get; set; }
    public int? ParentLocationID { get; set; }
    public string LocationName { get; set; }
    public string LocationName2 { get; set; }
    public int LocationID { get; set; }
    public virtual Address Address { get; set; }
}

错误是：

LINQ to Entities不会识别该方法，并且此方法无法转换为存储表达式。

推荐答案

你可以尝试这个..

 public IEnumerable<Location> GetChild(int id)
        {
            DBEntities db = new DBEntities();
        var locations = db.Locations.Where(x => x.ParentLocationID == id || x.LocationID == id).ToList();

    var child = locations.AsEnumerable().Union(
                                db.Locations.AsEnumerable().Where(x => x.ParentLocationID == id).SelectMany(y => GetChild(y.LocationId))).ToList();
            return child;
        }

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