0

如果我有以下列表

List<FlatObject> objects = new List<FlatObject>();

objects.Add(new FlatObject { ID = 1, ParentID = 0, Name = "January", Amount = 1000 });          
objects.Add(new FlatObject { ID = 2, ParentID = 0, Name = "February", Amount = 2000 });        
objects.Add(new FlatObject { ID = 3, ParentID = 0, Name = "March", Amount = 3000 });    
objects.Add(new FlatObject { ID = 4, ParentID = 0, Name = "April", Amount = 4000 });    
objects.Add(new FlatObject { ID = 5, ParentID = 0, Name = "May", Amount = 5000 });
objects.Add(new FlatObject { ID = 6, ParentID = 1, Name = "June", Amount = 6000 });
objects.Add(new FlatObject { ID = 7, ParentID = 1, Name = "July", Amount = 7000 });
objects.Add(new FlatObject { ID = 8, ParentID = 1, Name = "August", Amount = 8000 }); 
objects.Add(new FlatObject { ID = 9, ParentID = 2, Name = "September", Amount = 9000 }); 
objects.Add(new FlatObject { ID = 10, ParentID = 2, Name = "October", Amount = 10000 });
objects.Add(new FlatObject { ID = 11, ParentID = 2, Name = "November", Amount = 11000 });
objects.Add(new FlatObject { ID = 12, ParentID = 10, Name = "December", Amount = 12000 });
objects.Add(new FlatObject { ID = 13, ParentID = 10, Name = "January", Amount = 13000 }); 
objects.Add(new FlatObject { ID = 14, ParentID = 10, Name = "February", Amount = 14000 });
objects.Add(new FlatObject { ID = 15, ParentID = 3, Name = "March", Amount = 15000 });
objects.Add(new FlatObject { ID = 16, ParentID = 3, Name = "April", Amount = 16000 });
objects.Add(new FlatObject { ID = 17, ParentID = 3, Name = "May", Amount = 17000 });

有谁知道我如何编写一个返回对象列表及其所有递归子对象列表的函数？

例如，如果我输入 id = 2 的参数，我想返回

FlatObject { ID = 2, ParentID = 0, Name = "February", Amount = 2000 });     
FlatObject { ID = 9, ParentID = 2, Name = "September", Amount = 9000 });
FlatObject { ID = 10, ParentID = 2, Name = "October", Amount = 10000 });
FlatObject { ID = 11, ParentID = 2, Name = "November", Amount = 11000 });
FlatObject { ID = 12, ParentID = 10, Name = "December", Amount = 12000 });
FlatObject { ID = 13, ParentID = 10, Name = "January", Amount = 13000 });
FlatObject { ID = 14, ParentID = 10, Name = "February", Amount = 14000 });

在列表中；

如果我要找回孩子，我知道如何使用 LINQ 做到这一点，但如果我要找回孩子和后代，我就不知道了。

4

3 回答 3

1

您可以在高级别的使用递归函数，如下所示，

private List<int> GetAllChildren(int parent)
{
    List<T> children = new List<T>();
    PopulateChildren(parent.ID, children);
    return children;
}

private void PopulateChildren(int parent, List<int> children)
{

    //look up immediate childs and pass each child to recursice method and add child to list
}
于 2013-10-10T11:50:16.887 回答
1

假设 ID 始终是唯一的，非零父 ID 在集合中始终具有相应的对象，并且所有根对象的 ParentID 都为零，您可以创建一个扩展方法来回答某个对象是具有某个 ID 的对象的子对象还是孙子对象：

public static bool HasAncestor(this FlatObject obj, IEnumerable<FlatObject> objs, int id)
{
    if (obj.ID == id)
       return true;
    if (obj.ParentID == 0)
       return false;
    return objs.Single(o => o.ID == obj.ParentID)  // Get parent
               .HasAncestor(objs, id);             // recurse
}

鉴于您也可以以其他方式使用它，获取具有某个祖先的所有对象

public static IEnumerable<FlatObject> GetAllChildren(this FlatObject obj, IEnumerable<FlatObject> objs)
{
    return objs.Where(o => o.HasAncestor(objs, obj.ID));
}
于 2013-10-10T11:57:17.470 回答
0

Here is your complete solution (Tested). Just add FlatObjectExtention to your solution.

class Program
{
    static void Main(string[] args)
    {
        List<FlatObject> objects = new List<FlatObject>();

        objects.Add(new FlatObject { ID = 1, ParentID = 0, Name = "January", Amount = 1000 });
        objects.Add(new FlatObject { ID = 2, ParentID = 0, Name = "February", Amount = 2000 });
        objects.Add(new FlatObject { ID = 3, ParentID = 0, Name = "March", Amount = 3000 });
        objects.Add(new FlatObject { ID = 4, ParentID = 0, Name = "April", Amount = 4000 });
        objects.Add(new FlatObject { ID = 5, ParentID = 0, Name = "May", Amount = 5000 });
        objects.Add(new FlatObject { ID = 6, ParentID = 1, Name = "June", Amount = 6000 });
        objects.Add(new FlatObject { ID = 7, ParentID = 1, Name = "July", Amount = 7000 });
        objects.Add(new FlatObject { ID = 8, ParentID = 1, Name = "August", Amount = 8000 });
        objects.Add(new FlatObject { ID = 9, ParentID = 2, Name = "September", Amount = 9000 });
        objects.Add(new FlatObject { ID = 10, ParentID = 2, Name = "October", Amount = 10000 });
        objects.Add(new FlatObject { ID = 11, ParentID = 2, Name = "November", Amount = 11000 });
        objects.Add(new FlatObject { ID = 12, ParentID = 10, Name = "December", Amount = 12000 });
        objects.Add(new FlatObject { ID = 13, ParentID = 10, Name = "January", Amount = 13000 });
        objects.Add(new FlatObject { ID = 14, ParentID = 10, Name = "February", Amount = 14000 });
        objects.Add(new FlatObject { ID = 15, ParentID = 3, Name = "March", Amount = 15000 });
        objects.Add(new FlatObject { ID = 16, ParentID = 3, Name = "April", Amount = 16000 });
        objects.Add(new FlatObject { ID = 17, ParentID = 3, Name = "May", Amount = 17000 });

        objects.First(x=>x.ID==2).GetAllChildren(objects).ToList().ForEach(Console.WriteLine);

        Console.ReadKey();
    }
}

public class FlatObject
{
    public int ID { get; set; }
    public int ParentID { get; set; }
    public string Name { get; set; }
    public int Amount { get; set; }

    public override string ToString()
    {
        return string.Format("ID={0} ParentID={1} Name={2} Amount={3} ", ID, ParentID, Name, Amount);
    }
}

public static class FlatObjectExtention
{
    public static IList<FlatObject> GetAllChildren(this FlatObject flatObject, IList<FlatObject> allItems)
    {
        var allChildren = new List<FlatObject>();
        var children = allItems.Where(x => x.ParentID == flatObject.ID).ToList();
        allChildren.AddRange(children);

        foreach (var child in children)
        {
            allChildren.AddRange(child.GetAllChildren(allItems));
        }
        return allChildren;
    }
}
于 2013-10-10T12:57:35.570 回答