Global.asax.cs

using System;
using System.Web;
using System.Web.Helpers;

namespace SitefinityWebApp
{
    public class Global : System.Web.HttpApplication
    {

        protected void Application_Start(object sender, EventArgs e)
        {
            // Workaround for the following issue
            // https://knowledgebase.progress.com/articles/Article/this-operation-requires-iis-integrated-pipeline-mode-error-when-using-antiforgerytoken

            AntiForgeryConfig.SuppressXFrameOptionsHeader = true;
        }

        protected void Session_Start(object sender, EventArgs e)
        {

        }

        protected void Application_BeginRequest(object sender, EventArgs e)
        {
            HttpContext.Current.Response.AddHeader("X-Frame-Options", "SAMEORIGIN");
        }

        protected void Application_AuthenticateRequest(object sender, EventArgs e)
        {

        }

        protected void Application_Error(object sender, EventArgs e)
        {

        }

        protected void Session_End(object sender, EventArgs e)
        {

        }

        protected void Application_End(object sender, EventArgs e)
        {

        }
    }
}