Master does not have a definition for ViewData (ASP.NET MVC2)

I’m building an ASP.NET MVC2 web application and I was trying to access ViewData in my Site.Master page and I kept getting “master does not have a definition for ViewData”.

<%= ViewData["topic"] %>

The simple answer was that my Master Page was not an ASP.NET MVC2 master page. Somehow I had a standard master page.

So, all I did was swap the existing page declaration

<%@ Master Language="C#" AutoEventWireup="true" CodeBehind="Site.Master.cs" Inherits="HubSubscriber.Views.Shared.Site" %>

With an ASP.NET MVC2 declaration:

<%@ Master Language="C#" Inherits="System.Web.Mvc.ViewMasterPage" %>

And bingo! ViewData was now accessible from my master page.

This post on Passing Data to View Master Pages may also be useful.

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