NullReferenceException in C# windows form application

Hi,

Given below is my code.. I am getting "Null reference exception" in the very first line.

HttpResponse response =HttpContext.Current.Response;
response.Clear();
response.ClearContent();
response.ClearHeaders();

I am working in windows form application. I am using this line to export a gridview data to excel with SaveAs(browse) option.

Pease suggest.

Thanks.