ASP.NET MVC StackOverflowException Loading dynamic menu from xml in Layout

Question

I try to put a dynamic menu (load from xml) in my Layout but I've got a StackOverflowException in PartialController.cs/MainMenu()

I don't understand why my code throw a StackOverflowException because I don't have a loop (or I don't see it !).

Layout.cshtml :

....
<div id="menu">
    @if (Request.IsAuthenticated)
    {
        Html.RenderAction("MainMenu", "Partial");
    }
</div>
....

MainMenu.cshtml :

@model Geosys.BoT.Portal.POC.Business.Menu

@foreach (var item in Model.Nodes)
{
    <ul>
        <li>
            @item.Name
            <ul>
                @foreach (var subItem in item.Links)
                {
                    <li>
                        @Html.ActionLink(subItem.Name, subItem.Action, subItem.Controller)
                    </li>
                }
            </ul>
        </li>
    </ul>
}

PartialController.cs :

[ChildActionOnly]
public ActionResult MainMenu()
{
    var menu = new Menu { Nodes = new List<NodeMenu>() };

    var xmlData = System.Web.HttpContext.Current.Server.MapPath("~/Content/navigation.xml");
    if (xmlData == null)
    {
        throw new ArgumentNullException("xmlData");
    }

    var xmldoc = new XmlDataDocument();

    var fs = new FileStream(xmlData, FileMode.Open, FileAccess.Read);
    xmldoc.Load(fs);

    var xmlnode = xmldoc.GetElementsByTagName("node");

    for (var i = 0; i <= xmlnode.Count - 1; i++)
    {
        var xmlAttributeCollection = xmlnode[i].Attributes;

        if (xmlAttributeCollection != null)
        {
            var nodeMenu = new NodeMenu { Name = xmlAttributeCollection["title"].Value, Links = new List<LinkMenu>() };

            if (xmlnode[i].ChildNodes.Count != 0)
            {
                for (var j = 0; j < xmlnode[i].ChildNodes.Count; j++)
                {
                    var linkMenu = new LinkMenu();

                    var xmlNode = xmlnode[i].ChildNodes.Item(j);
                    if (xmlNode != null)
                    {
                        if (xmlNode.Attributes != null)
                        {
                            linkMenu.Name = xmlNode.Attributes["title"].Value;
                            linkMenu.Action = xmlNode.Attributes["action"].Value;
                            linkMenu.Controller = xmlNode.Attributes["controller"].Value;
                            linkMenu.Key = xmlNode.Attributes["key"].Value;

                            nodeMenu.Links.Add(linkMenu);
                        }
                    }
                }
            }

            menu.Nodes.Add(nodeMenu);
        }
    }
    return View(menu);
}

navigation.xml:

<nodes>
  <node title="User Management">
    <link title="Create User" action="CreateUser" controller="UserManagement" key="UM_CREATEUSER" />
    <link title="Users List" action="UsersList" controller="UserManagement" key="UM_USERSLIST" />
    <link title="Import Users" action="ImportUsers" controller="UserManagement" key="UM_IMPORTUSERS" />
  </node>
</nodes>

EDIT : This is the detail of the exception (there's no StackTrace):

System.StackOverflowException was unhandled An unhandled exception of type 'System.StackOverflowException' occurred in mscorlib.dll

{Cannot evaluate expression because the current thread is in a stack overflow state.}

In the Call Stack, I see the line "Html.RenderAction("MainMenu", "Partial");" constantly called but I don't know why.

What do you mean, I see 3 loops in this code. 1 foreach loop and 2 for loops. If you can add the stack trace from the overflow exception, that may help narrow down where the stack is overflowing. — danludwig
– danludwig, Commented Dec 4, 2014 at 15:49
You may try LINQ expression to get list of selected nodes instead of loops ( if you need help on that, let me know). Side note: Finally saw stackoverflow exception in stackoverflow.com :) . — Arindam Nayak
– Arindam Nayak, Commented Dec 4, 2014 at 15:54
When I say "I don't see a loop", I mean I don't see a recursive loop. I know I've got 3 loops but the stackoverflow exception isn't in these loops. The MainMenu() method is called several times. I'll put the stacktrace in the main. — Pierre-Antoine DOUCHET
– Pierre-Antoine DOUCHET, Commented Dec 5, 2014 at 8:24

Erik Funkenbusch · Accepted Answer · 2015-04-02 02:43:38Z

3

There is an infinite loop here. The problem is that you do this in your Layout:

@Html.RenderAction("MainMenu", "Partial");

And then in your Action you do this:

return View(menu);

When you call return View() your view is rendered, including your layout. So your layout then renders your @Html.RenderAction(...) again... which calls your View()... which renders your Layout... etc.. etc.. etc..

You solve this by returning a PartialView() which does not render your Layout, or by rendering a view with Layout set to Null. This is the primary difference between a View() and a PartialView(), Layout rendering.

edited Apr 2, 2015 at 2:43

answered Dec 6, 2014 at 5:03

Erik Funkenbusch

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1 Comment

realmikep Over a year ago

I've found this solution in other places on SO, but you're the only one that explained why. Thanks!

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