Server cannot set content type after HTTP headers have been sent. in asp.net

Following error occure while printing the ascx in pdf.
Error caught in Application_Error event Error in: http://localhost:1849/de/header-navigation-node/onlineshop/mein-konto Error message: Server cannot set content type after HTTP headers have been sent. Stack trace: at System.Web.HttpResponse.set_ContentType(String value) at System.Web.HttpResponseInternalWrapper.set_ContentType(String value) at System.Web.UI.PageRequestManager.RenderPageCallback(HtmlTextWriter writer, Control pageControl) at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) at System.Web.UI.Page.Render(HtmlTextWriter writer) at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) at System.Web.UI.Control.RenderControl(Ht ...