README.md

Catch all 404 errors in an ASP.NET MVC application with the following code. Solution found via Stack Overflow http://stackoverflow.com/questions/717628/asp-net-mvc-404-error-handling

ErrorController.cs

public ActionResult NotFound()
{
    ActionResult result;

    object model = Request.Url.PathAndQuery;

    if (!Request.IsAjaxRequest())
    {
        result = View("NotFound", model);
    }
    else
    {
        result = PartialView("NotFound", model);
    }

    return result;
}

Global.asax.cs

protected void Application_EndRequest()
{
    if (Context.Response.StatusCode == 404)
    {
        Response.Clear();

        var rd = new RouteData();
        rd.Values["controller"] = "Errors";
        rd.Values["action"] = "NotFound";

        IController c = new ErrorController();
        c.Execute(new RequestContext(new HttpContextWrapper(Context), rd));
    }
}