Question

Please can anybody point out where this code might be going wrong. I am trying to create a partial class for the masterpage.

The master pages class:

namespace MuniWeb.Models.SiteMaster{  public class BaseViewData {     public string Title { get; set; }     public string MetaKeywords { get; set; }     public string MetaDescription { get; set; } }  public partial class Site : System.Web.Mvc.ViewMasterPage<MuniWeb.Models.SiteMaster.BaseViewData> {     public Site()     {         ViewData.Model = new BaseViewData();     } }} 

The master page:

<%@ Master Language='C#' Inherits='System.Web.Mvc.ViewMasterPage<MuniWeb.Models.SiteMaster.BaseViewData>' %> 

The error:

Object reference not set to an instance of an object. Line 33:             <div id='footer'> Line 34:                 ApplicationID: Line 35:                 <%= Model.Title %> Line 36:             </div> Line 37:         </div> 

I am just using this as an example. The code I want to use needs to fire for every page to check certain parameters, this is why it is in the master page.

Answer 1

You shouldn’t need to make a partial class. What does your controllers action code look like? The error looks like it could be from not handing the View (and therefore it’s master page) a model.

Try something like this:

namespace MuniWeb.Website.ViewDataModels {      public class BaseViewData     {         public string Title { get; set; }         public string MetaKeywords { get; set; }         public string MetaDescription { get; set; }     }      public class SubViewData : BaseViewData     {         public IList<Thing> Things { get; set; }     } } 

Then define your master page like you had:

<%@ Master Language='C#' Inherits='System.Web.Mvc.ViewMasterPage<MuniWeb.Website.ViewDataModels.BaseViewData>' %> 

Now in your controller

public ActionResult Index() {     SubViewData viewData = new SubViewData();     viewData.Title = 'Page Title';     viewData.MetaKeywords = 'This, that, and the other';     viewData.MetaDescription = 'A really great page about this, that, and the other.';      viewData.Things = _myRepository.GetThings();      return View(viewData); } 

See how that goes…

I would ask why the MasterPage NEEDS strongly type ViewData. I understand that yes, sometimes strongly typed viewdata is needed in masterpages but generally you should be able to get way with just using the ViewData name value collection.