Asp.net mvc4 Partial view with model in Layout

Question

I am trying to create the menus in my _Layout page using a partial view called _Menus which reads from a Json file on my server. But I can't figure out how to call a partial view with a model from the layout page.

Here is the _Menu.cshtml page, which is in the Shared folder:

@model IEnumerable<LangSite_151209.Models.MenuItem>

<div id="menu" class="largescreen_show smallscreen_hide" data-display="flex">
    <div id="menu_left" class="menu_item">

        @foreach (var mainMenuItem in Model)
        {
           // A bunch of stuff with the model that draws the menu
        }
   </div>
</div>

Here is how I call it in the _Layout page:

<!DOCTYPE html>

<html lang="en">
<head>
     <!-- Meta and script stuff -->
</head>
<body style="overflow:hidden;"> 


    <div id="fg">

        <div id="mobile_wrapper">
        @Html.Partial("../Shared/_Menu")
        </div>

    </div>
    <!-- A bunch of footer stuff that's irrelevant here -->
</html>

I have tried returning the partial view with a SharedController that opens the Json file and turns it into a model for the partial, as follows:

public class SharedController : Controller
{
    // GET: Shared
    [ChildActionOnly]
    public ActionResult _Menu()
    {
        string filePath = HostingEnvironment.MapPath(@"~/App_Data/MenuItems.json");
        StreamReader sr = new StreamReader(filePath);

        string JsonString = sr.ReadToEnd();
        JsonSerializerSettings settings = new JsonSerializerSettings
        {
            TypeNameHandling = TypeNameHandling.All
        };
        var menuItems = JsonConvert.DeserializeObject<List<MenuItem>>(JsonString, settings);

        return View(menuItems.ToList());
    }       
}

But when I try this I get a NullReferenceException on the Model: "Object reference not set to an instance of an object." Apparently you can't pass a model to a partial that way. I know that the code that reads the Json object works because when I use it the same code on a regular (non-partial) page it passes the model correctly and the script draws the menu.

Normally if I want to pass a model to a partial I just put the model in the main page and pass it that way. But I don't know how to put a model in the _Layout. Is that how I should to it? Or is there a better way?

You can pass the model to a partial like this: @Html.Partial("viewName", Model). The problem is that the model has to be already populated. — Marko
– Marko, Commented Apr 12, 2016 at 18:58

Shyju · Accepted Answer · 2016-04-12 19:05:49Z

3

The line @Html.Partial("../Shared/_Menu") will not execute your _Menu action method. Your _Menu.cshtml partial view is strongly typed to a list of MenuItem's. So either you should explicitly pass it when calling the Html.Partial method or your the main view ( which is calling this partial) should be also typed to the same collection.

You should use Html.Action method instead of Html.Partial.

@Html.Action("_Menu", "Shared")

This will execute the _Menu action method and pass the needed data (list of MenuItem) to the corresponding partial view.

edited Apr 12, 2016 at 19:05

answered Apr 12, 2016 at 18:56

Shyju

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2 Comments

jimboweb Over a year ago

This makes the controller code work, thanks. Now I'm getting the error: "An unhandled exception of type 'System.StackOverflowException' occurred in mscorlib.dll" on the line: string filePath = HostingEnvironment.MapPath(@"~/App_Data/MenuItems.json");

jimboweb Over a year ago

But that might be a different question.

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