Asp – Execute Code on Every Request

I see two options:

First:

Set the ViewData for MasterPage in YourBaseController.OnActionExecuting() or YourBaseController.OnActionExecuted():

public class YourBaseController : Controller
{
    protected override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        // Optional: Work only for GET request
        if (filterContext.RequestContext.HttpContext.Request.RequestType != "GET")
            return;

        // Optional: Do not work with AjaxRequests
        if (filterContext.RequestContext.HttpContext.Request.IsAjaxRequest())
            return;

        ...

        filterContext.Controller.ViewData["foo"] = ...
    }
}

Second:

Or create custom filter:

public class DataForMasterPageAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        // Optional: Work only for GET request
        if (filterContext.RequestContext.HttpContext.Request.RequestType != "GET")
            return;

        // Optional: Do not work with AjaxRequests
        if (filterContext.RequestContext.HttpContext.Request.IsAjaxRequest())
            return;

        ...

        filterContext.Controller.ViewData["foo"] = ...
    }
}

and then apply to your controllers:

[DataForMasterPage]
public class YourController : YourBaseController
{
    ...
}

I think the second solution is exactly for your case.

I'm not sure I follow exactly what you're trying to do, but if your view is using values in the route to display certain information, it seems like adding your own extension methods for HtmlHelper would be a better way to go.

Are Name, Language and Category contained in your routes? If so, then HtmlHelper will have access to the route info and can determine what to display via the extension methods. What is the correlation between your routes and what your views need to know?

Update: Is lang part of your route? If so, then I would still contend that you could write an HtmlHelper extension method that looks at the route data directly and determines which partial view to render. That way your controller wouldn't even need to worry about setting the ViewData["lang"]. The view would always know how to render based on the route.

Update 2: I think dismissing use of an HtmlHelper extension method because it re-evaluates the route data might be a case of premature optimization. Your controller inheritance scheme sounds overly complex and you asked the question because the way you were setting ViewData was unreliable. I doubt that pulling the value from route data would be much, if any, less efficient than setting and reading from ViewData.

From your comment:

In the controller I use the lang value to determine which view to show as well.

That only makes me think that there are more pieces of your system that I'd need to see in order to give better advice. If you have separate views for each language then why does the view need to be told which language to use?

Another alternative to consider would be using nested master pages. You could have a single master page for your site layout and then a nested master page for each language that just contains a hard coded lang value.