asp.net databound menu multilevel

Question

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

Answer 1

Here's one way you could do it.

• Represent parent/child relationship in your table with an adjacency list
• Map that adjacency list into a tree structure
• Convert that tree structure into your structure of menu items

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.

But anyway...

Default.aspx

<%@ Page Language="C#" Inherits="MenuTreeDemo.Default" %>



    


    

        
    

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();
            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 Children { get; set; }


        public MenuNode ()
        {
            Children = new List();
        }


        // 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;
        }
    }
}