Argentini.Halide.H3HttpModule.context_Error C# (CSharp) Method

        void context_Error(object sender, EventArgs e)
        {
            HttpApplication app = (HttpApplication)sender;
            Exception lastError = app.Server.GetLastError();
            HttpException he = lastError as HttpException;

            // handling only HttpExceptions (and 404 in particular):
            if (he != null)
            {
                int httpErrorCode = he.GetHttpCode();

                if (httpErrorCode == 404)
                {
                    // clearing the error in order to avoid the exception to be thrown:
                    app.Server.ClearError();
                    String fofPage = H3Config.GetKeyAsString("Error404Page", "", "Argentini.Halide");

                    // setting/changing the handler for the current response:
                    app.Context.Handler = System.Web.UI.PageParser.GetCompiledPageInstance(fofPage, app.Server.MapPath(fofPage), app.Context);
                }
            }
        }