public class ErrorController : baseController
{
    /// <summary>
    /// Displays a generic error message
    /// </summary>
    /// <param name="title"></param>
    /// <param name="message"></param>
    /// <param name="redirectTo"></param>
    /// <returns></returns>
    public ActionResult ShowError(string title, string message, string redirectTo, bool messageIsHtml)
    {
        if (string.IsNullOrEmpty(title))
            title = "An error occurred.";
 
        if (string.IsNullOrEmpty(message))
            message = "We are sorry, but an unspecified error occurred in the application. The error has been logged and forwarded to be checked out as soon as possible.";
 
        ErrorViewModel model = new ErrorViewModel
        {
            Message = message,
            Title = title,
            RedirectTo = redirectTo,
            MessageIsHtml = messageIsHtml
        };
 
        // Explicitly point at Error View regardless of action
        return View("Error", model);
    }
 
    public ActionResult ShowMessage(string title, string message, string redirectTo, bool messageIsHtml)
    {
        return this.ShowError(title, message, redirectTo, messageIsHtml);
    }
 
    /// <summary>
    /// Static method that can be called from outside of MVC requests
    /// (like in Application_Error) to display an error View.
    /// </summary>
    /// <param name="title"></param>
    /// <param name="message"></param>
    /// <param name="redirectTo"></param>
    /// <param name="messageIsHtml"></param>
    public static void ShowErrorPage(string title, string message, string redirectTo)
    {
        ErrorController controller = new ErrorController();
 
        RouteData routeData = new RouteData();
        routeData.Values.Add("controller", "Error");
        routeData.Values.Add("action", "ShowError");
        routeData.Values.Add("title", title);
        routeData.Values.Add("message", message);
        routeData.Values.Add("messageIsHtml", true);
 
        ((IController)controller).Execute(new RequestContext(new HttpContextWrapper(System.Web.HttpContext.Current), routeData));
    }
 
    /// <summary>
    /// Static method that can be called from outside of MVC requests
    /// (like in Application_Error) to display an error View.
    /// </summary>
    public static void ShowErrorPage(string title, string message)
    {
        ShowErrorPage(title, message, null);
    }
}
 
public class ErrorViewModel
{
    public string Title = string.Empty;
    public string Message = string.Empty;
    public string RedirectTo = string.Empty;
    public bool MessageIsHtml = false;
}
 
// call like this (for example in Application_Error
ErrorController.ShowErrorPage("Access Denied",
               "You've accessed a resource that requires a valid login. " +
               StockMessage);