Handle errors in global.asax

Global.asax.cs

 protected void Application_Error(object sender, EventArgs e)
        {
            Exception exception = Server.GetLastError();
            HttpException httpException = exception as HttpException;

            var configuration = WebConfigurationManager.OpenWebConfiguration("~/Web.config");
            CustomErrorsSection customErrors = (CustomErrorsSection)configuration.GetSection("system.web/customErrors");

            // if redirect mode 
            if (customErrors != null &&
                (
                    customErrors.Mode == CustomErrorsMode.Off ||
                    customErrors.RedirectMode == CustomErrorsRedirectMode.ResponseRedirect ||
                    (customErrors.RedirectMode == CustomErrorsRedirectMode.ResponseRewrite && customErrors.Mode == CustomErrorsMode.RemoteOnly && Request.IsLocal)
                )
            )
            {
                return;
            }

            /// Handle rewrite mode
            IHtmlErrorPageHelper errorPages = null;

            try
            {
                errorPages = EPiServer.ServiceLocation.ServiceLocator.Current.GetInstance<IHtmlErrorPageHelper>();
            }
            catch { }

            if (errorPages == null)
                return;

            RouteData routeData = new RouteData();
            string controller = string.Empty, action = string.Empty;

            if (httpException == null) // default to 500
            {
                controller = errorPages.ServerErrorControllerName;
                action = errorPages.ServerErrorControllerAction;
            }
            else
            {
                switch (httpException.GetHttpCode())
                {
                    case 403:
                        // Not Authorized.
                        controller = errorPages.ForbiddenControllerName;
                        action = errorPages.ForbiddenControllerAction;
                        break;
                    case 404:
                        // Page not found.
                        controller = errorPages.NotFoundControllerName;
                        action = errorPages.NotFoundControllerAction;
                        break;
                    case 500:
                    default:
                        // Server error.
                        controller = errorPages.ServerErrorControllerName;
                        action = errorPages.ServerErrorControllerAction;
                        break;
                }
            }

            if (string.IsNullOrWhiteSpace(controller) || string.IsNullOrWhiteSpace(action))
                return;

            IController errorController = null;
            RequestContext context = new RequestContext(new HttpContextWrapper(Context), routeData);

            try
            {
                // set route controller, action, and exception
                routeData.Values.Add("controller", controller);
                routeData.Values.Add("action", action);
                routeData.Values.Add("error", exception);

                // Create target Controller and pass the routeData.
                IControllerFactory factory = ControllerBuilder.Current.GetControllerFactory();
                errorController = factory.CreateController(context, controller);

            }
            catch
            {
                return; // allow defaults to occur
            }

            // Clear the error on server.
            Server.ClearError();

            // Avoid IIS7 getting in the middle
            Response.TrySkipIisCustomErrors = true;

            // clear the content
            Response.Clear();

            // execute new content
            errorController.Execute(context);

            // Call target Controller and pass the routeData.
            //IController errorHandler = new WSOL.Web.Controllers.ErrorController();
            //errorHandler.Execute(new RequestContext(new HttpContextWrapper(Context), routeData));
        } 

IHtmlErrorPageHelper.cs

namespace WSOL.EPiServerCms.Web.Interfaces
{
    //
    // Summary:
    //     Define Routes, controllers and actions
    public interface IHtmlErrorPageHelper
    {
        //
        // Summary:
        //     Forbidden controller action
        string ForbiddenControllerAction { get; }
        //
        // Summary:
        //     Forbidden controller name
        string ForbiddenControllerName { get; }
        //
        // Summary:
        //     Forbidden controller route
        string ForbiddenControllerRoute { get; }
        //
        // Summary:
        //     Not found controller action
        string NotFoundControllerAction { get; }
        //
        // Summary:
        //     Not found controller name
        string NotFoundControllerName { get; }
        //
        // Summary:
        //     Not found route
        string NotFoundControllerRoute { get; }
        //
        // Summary:
        //     Server error controller
        string ServerErrorControllerAction { get; }
        //
        // Summary:
        //     Server error controller name
        string ServerErrorControllerName { get; }
        //
        // Summary:
        //     Server error route
        string ServerErrorControllerRoute { get; }
    }
}