How to call a generic handler from Code behind C#

string handlerUrl = String.Format(Request.Url.Scheme+"://" +Request.Url.Authority+"{0}","/Handler.ashx");

        string response = (new WebClient()).DownloadString(handlerUrl);

https://www.aspsnippets.com/Articles/1671/ASPNet-Call-Execute-Generic-HTTP-Handler-from-Code-Behind-using-C-and-VBNet/

 https://stackoverflow.com/questions/11535754/how-to-call-httphandler-from-cs-file-asp-net