RenderPartial Problem (While sending data to master page)

I am trying to send some data the master page. I am using Razor as my View Engine, and AutoMapper to map between Domain and View Models. Below is my code:

//the partial view action method:
public ActionResult RenderCategories()
{
    IEnumerable<TopLevelCategory> categories = _categoryService.GetTopLevelCategories();
    var viewModel = new MasterPageViewModel
                    {
                        Categories =
                            Mapper.Map
                            <IEnumerable<TopLevelCategory>, IEnumerable<ParentCategory>>(categories)
                    };

    return View(viewModel);
}

//the partial view file: (this is just a test for now)
@model S开发者_如何转开发harwe.MVC.ViewModels.MasterPageViewModel

@foreach (var item in Model.Categories) {
      @item.Name
}

public class MasterPageViewModel
{
    public IEnumerable<ParentCategory> Categories { get; set; }
}

I'm calling the partial view using @Html.RenderPartial("RenderCategories") from inside my _Layout.cshtml file. But I keep getting the following error:

Compiler Error Message: CS1502: The best overloaded method match for 'System.Web.WebPages.WebPageExecutingBase.Write(System.Web.WebPages.HelperResult)' has some invalid arguments

What's going on?

---

The RenderPartial extension method writes directly to the output stream and has no return type (void). So here's the correct syntax to call it:

@{Html.RenderPartial("RenderCategories");}

or if you prefer you could use the Partial extension method:

@Html.Partial("RenderCategories")

Contrast those with their equivalents in the WebForms view engine:

<% Html.RenderPartial("RenderCategories"); %>
<%= Html.Partial("RenderCategories") %>