问题描述
我目前正在使用 asp.net 菜单控件从表父/子项加载.我遇到的问题是，如果孩子有另一个孩子.从这个意义上说，我的代码有点静态，我似乎找不到更好的或该"的方法来做到这一点.我已经将站点地图视为数据源，但我不需要站点地图，并且觉得这对于我需要实现的目标来说太过分了.
I am currently using an asp.net menu control to load from a table parent/child items. The problem I am having is that if the child has another child. My code is kindof static in that sense and I can't seem to find a better or "the" way to do it. I have seen sitemap as datasources but i don't need a sitemap and feel that would just be overkill for what I need to achieve.
foreach (ClassName option in list)
{
MenuItem module = new MenuItem(option.Description.ToLower(), "", "", option.Url + "?option=" + option.Optionid);
module.Selectable = true;
navigation.Items.Add(module);
//this is my second level
foreach (ClassName child in listfromparent(option.Optionid))
{
MenuItem childmenu = new MenuItem(child.Description.ToLower(), "", "", child.Url + "?option=" + child.Optionid);
module.ChildItems.Add(childmenu);
}
}
如您所见，这适用于 2 个级别:(当然，我可以在 child 中放置另一个 childlevel 来创建第 3 个级别，但是如果有第 4 个、第 5 个呢?所以这就是为什么我需要它自己做.我注意到 treeview 有 onpopulate 但显然 Menu 没有.提前致谢.
as you can see this works but for 2 levels :( and of course i could put another childlevel inside child to create the 3rd level but what if there is a 4th, 5th? So that's why I need it to do it itself. I noticed treeview has onpopulate but apparently Menu doesn't. Thanks in advance.
推荐答案
这是您可以做到的一种方法.
Here's one way you could do it.
- 用邻接表表示表中的父/子关系
- 将该邻接表映射为树状结构
- 将该树结构转换为您的菜单项结构
也许您可以跳过中间步骤，将邻接列表直接映射到 MenuItems 树，也许可以在 MenuItem 上使用一些扩展方法.
Maybe you could skip that middle step and map the adjacency list straight to a tree of MenuItems, maybe with some extension methods on MenuItem.
但无论如何...
Default.aspx
<%@ Page Language="C#" Inherits="MenuTreeDemo.Default" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
<head runat="server">
<title>Default</title>
</head>
<body>
<form id="form1" runat="server">
<asp:Menu ID="MyMenu" runat="server" StaticDisplayLevels="3" />
</form>
</body>
</html>
Default.aspx.cs
using System;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Collections.Generic;
namespace MenuTreeDemo
{
public partial class Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
MenuNode root = ConvertTableToTree(GetTreeTable());
foreach (MenuNode topLevelNode in root.Children)
{
MyMenu.Items.Add(topLevelNode.ToMenuItem()); // Visits all nodes in the tree.
}
}
}
// The menu tree as an adjacency list in a table.
static DataTable GetTreeTable()
{
DataTable table = new DataTable();
table.Columns.Add("Id", typeof(int));
table.Columns.Add("Description", typeof(string));
table.Columns.Add("Url", typeof(string));
table.Columns.Add("ParentId", typeof(int));
table.Rows.Add(1, "TopMenu1", "/foo.html", 0);
table.Rows.Add(2, "SubMenu1.1", "/baz.html", 1);
table.Rows.Add(3, "SubMenu1.2", "/barry.html", 1);
table.Rows.Add(4, "SubMenu1.2.1", "/skeet.html", 3);
table.Rows.Add(5, "TopMenu2", "/bar.html", 0);
table.Rows.Add(6, "TopMenu3", "/bar.html", 0);
table.Rows.Add(7, "SubMenu3.1", "/ack.html", 6);
return table;
}
// See e.g. http://stackoverflow.com/questions/2654627/most-efficient-way-of-creating-tree-from-adjacency-list
// Assuming table is ordered.
static MenuNode ConvertTableToTree(DataTable table)
{
var map = new Dictionary<int, MenuNode>();
map[0] = new MenuNode() { Id = 0 }; // root node
foreach (DataRow row in table.Rows)
{
int nodeId = int.Parse(row["Id"].ToString());
int parentId = int.Parse(row["ParentId"].ToString());
MenuNode newNode = MenuNodeFromDataRow(row);
map[parentId].Children.Add(newNode);
map[nodeId] = newNode;
}
return map[0]; // root node
}
static MenuNode MenuNodeFromDataRow(DataRow row)
{
int nodeId = int.Parse(row["Id"].ToString());
int parentId = int.Parse(row["ParentId"].ToString());
string description = row["Description"].ToString();
string url = row["Url"].ToString();
return new MenuNode() { Id=nodeId, ParentId=parentId, Description=description, Url=url };
}
}
}
MenuNode.cs
using System;
using System.Collections.Generic;
using System.Web.UI.WebControls;
namespace MenuTreeDemo
{
public class MenuNode
{
public int Id { get; set; }
public int ParentId { get; set; }
public string Description { get; set; }
public string Url { get; set; }
public List<MenuNode> Children { get; set; }
public MenuNode ()
{
Children = new List<MenuNode>();
}
// Will visit all descendants and turn them into menu items.
public MenuItem ToMenuItem()
{
MenuItem item = new MenuItem(Description) { NavigateUrl=Url };
foreach (MenuNode child in Children)
{
item.ChildItems.Add(child.ToMenuItem());
}
return item;
}
}
}
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