Recursive looping on a list MVC 3

I have a side menu in my site, which is currently a load of list items:

<ul>
    <li>...</li>
    <li>...</li>
    <li>...</li>
</ul>

Now I need to change this to have sub items, so that it renders...

<ul>
    <li>
        <ul>
            <li>...</li>
            <li>...</li>
        </ul>
    </li>
    <li>...</li>
    <li>...</li>
</ul>

I have a list of items like so:

    /// <summary>
    /// Gets the admin menu items.
    /// </summary>
    /// <returns></returns>
    public IQueryable<IAdminMenuItem> GetAdminMenuItems()
    {
        return new List<IAdminMenuItem> {              
            new AdminMenuItem {MenuItemId = "100", DisplayText = "xxx", ParentId = "" ControllerName = "xxx", ActionName = "xxx"},
            new AdminMenuItem {MenuItemId = "101", DisplayText = "xxx", ParentId = "100" ControllerName = "xxx", ActionName = "xxx"},
            new AdminMenuItem {MenuItemId = "102", DisplayText = "xxx", ParentId = "100" ControllerName = "xxx", ActionName = "xxx"},
            new AdminMenuItem {MenuItemId = "200", DisplayText = "xxx", ParentId = "" ControllerName = "xxx", ActionName = "xxx"},
            new AdminMenuItem {MenuItemId = "201", DisplayText = "xxx", ParentId = "200" ControllerName = "xxx", ActionName = "xxx"},
            new AdminMenuItem {MenuItemId = "202", DisplayText = "xxx", ParentId = "200" ControllerName = "xxx", ActionName = "xxx"},
        开发者_如何转开发}.AsQueryable();

If a list item doesn't have a ParentID then it is a top level element. If it does, it is a sub item element.

I've got this code in at present to cope with the flat menu structure:

<ul>
    @foreach (Avelo.Exchange.WebUI.Domain.Interfaces.IAdminMenuItem item in Model){
       <li><a href="@Url.Action(item.ActionName, item.ControllerName)"><span>@item.DisplayText</span></a></li>
    }
</ul>

I suppose my first question is how would I handle the sub menu items in the view, but I would also like to future proof the solution by it being able to handle further sub levels (i.e. three steps down rather than just two). I've heard of recursive looping, but have no idea how to implement it. Is this a good way to go?

Thanks in advance

S

I have had a similar problem some time ago. I'll try to adapt my solution to your model. I guess you have something like this:

public interface IAdminMenuItem
{
    string MenuItemId { get; set; }
    string DisplayText { get; set; }
    string ControllerName { get; set; }
    string ActionName { get; set; }
    List<IAdminMenuItem> Children { get; set; }
}

public class AdminMenuItem: IAdminMenuItem
{
    public string MenuItemId { get; set; }
    public string DisplayText { get; set; }
    public string ControllerName { get; set; }
    public string ActionName { get; set; }
    public List<IAdminMenuItem> Children { get; set; }
}

As you can see I've changed your property ParentId with a collection of Children cause it's easier to manage.

In your view you would populate your menu (and all the submenus) and pass it to the view:

List<IAdminMenuItem> myMenu = new List<IAdminMenuItem>();

myMenu.Add(new AdminMenuItem()
    {
    MenuItemId = "100",
    DisplayText = "Level 1",
    ControllerName = "Home",
    ActionName = "Index",
    Children = new List<IAdminMenuItem>() { 
        new AdminMenuItem() { MenuItemId = "1001", DisplayText = "Level 1a", ControllerName = "Home", ActionName = "Index" },
        new AdminMenuItem() { MenuItemId = "1002", DisplayText = "Level 1b", ControllerName = "Home", ActionName = "Index" }
    }
});

myMenu.Add(new AdminMenuItem()
    {
    MenuItemId = "200",
    DisplayText = "Level 2",
    ControllerName = "Home",
    ActionName = "Index",
    Children = new List<IAdminMenuItem>() { 
        new AdminMenuItem() { MenuItemId = "2001", DisplayText = "Level 2a", ControllerName = "Home", ActionName = "Index" },
        new AdminMenuItem() { MenuItemId = "2002", DisplayText = "Level 2b", ControllerName = "Home", ActionName = "Index" }
    }
});

return View(myMenu);

This is my view. There is not much in here.

@using Mvc3SubMenus.WebUI
@model List<Mvc3SubMenus.IAdminMenuItem>
@{
    ViewBag.Title = "Home Page";
}

@Html.BuildMenu(Model)

I've created an helper which will be in charge of creating your menu and all the submenus (with recursion):

using System.Collections.Generic;
using System.Web.Mvc;
using System.Text;
using System.Web.Mvc.Html;

namespace Mvc3SubMenus.WebUI
{
    public static class MyHelpers
    {
        public static System.Web.Mvc.MvcHtmlString BuildMenu(this HtmlHelper helper, List<Mvc3SubMenus.IAdminMenuItem> menu)
        {
            return new MvcHtmlString(BuildStringMenu(helper, menu));
        }

        private static string BuildStringMenu(HtmlHelper helper, List<Mvc3SubMenus.IAdminMenuItem> menu)
        {
            var sb = new StringBuilder();
            if ((menu != null) && (menu.Count > 0))
            {
                sb.Append("<ul>");
                foreach (var item in menu)
                {
                    sb.Append("<li>");
                    sb.Append(helper.ActionLink(item.DisplayText, item.ActionName, item.ControllerName));
                    sb.Append("</li>");
                    if ((item.Children != null) && (item.Children.Count > 0))
                    {
                        sb.Append("<li>");
                        sb.Append(BuildStringMenu(helper, item.Children));
                        sb.Append("</li>");
                    }
                }
                sb.Append("</ul>");
            }
            return (sb.ToString());
        }
    }
}

This helper can be improved and surely someone might object that it can be done in a better way but I didn't have much time to perfect it. Sorry for that.
You can find some code here. The project is called Mvc3SubMenus.