1

我为 MenuItem 定义了以下类

public class MenuItem
{
    public int Id { get; set; }
    public string Key { get; set; }     
    public int ParentId { get; set; }
    public string Url { get; set; }        
}

下面也是所有菜单项的集合

List<MenuItem> allMenu=new List<MenuItem>
  {new MenuItem{Id=1,Key="Level1-A",Url="url1"},
  {new MenuItem{Id=2,Key="Level1-B",Url="url2"},
  {new MenuItem{Id=3,Key="Level2-A",Url="url3", ParentId=1},
  {new MenuItem{Id=4,Key="Level3-AA",Url="url1", ParentId=3}};

现在我只有一个从数据库中检索到的菜单项，即Level3-AA

MenuItem item=new MenuItem{Id=4,Key="Level3-AA",Url="url1", ParentId=3};

 allMenu.FindAll(m=>m.Id==item.Id) //gives only one element Level3-AA

//但我还需要包含所有父 ID 菜单项。

在这种情况下Level2-A和Level1-A

如何在 C# 中包含它？欢迎使用 LINQ 或任何扩展方法

4

2 回答 2

2 
List<MenuItem> all = new List<MenuItem>();
all.Add(item);

while (item.ParentId != 0) // Ideally you should use Nullable<int>
{
    var parent = allMenu.Single(m => m.Id = item.ParentId);
    all.Add(parent);
    item = parent;
}

This will result in multiple queries to the database though. If you don't want this to happen you'll need to write your own SQL query with database features like recursive CTE.

于 2013-08-02T16:19:27.903 回答
0

更改 MenuItem，使其具有可为空的 parentId：

public class MenuItem
{
    public int Id { get; set; }
    public string Key { get; set; }
    public int? ParentId { get; set; }
    public string Url { get; set; }
}

使用此Node 类获取节点：

var allMenus=new List<MenuItem>
    {new MenuItem{Id=1,Key="Level1-A",Url="url1"},
    new MenuItem{Id=2,Key="Level1-B",Url="url2"},
    new MenuItem{Id=3,Key="Level2-A",Url="url3", ParentId=1},
    new MenuItem{Id=4,Key="Level3-AA",Url="url1", ParentId=3}};

// Creates trees based on Id and ParentId, 
// in this case there are 2 trees, the second with only item with Id 2
var rootNode = Node<MenuItem>.CreateTree(allMenus, m => m.Id, m => m.ParentId).First();

var targetNode = rootNode.Descendants.Single(n => n.Value.Id == 4);

现在你所要做的就是：

// Get the values of the ancestors (all the parents and their parents)
var ancestorValues = targetNode.Ancestors.Values();
于 2013-08-03T21:24:01.137 回答