google response code

I have a site in C#. I am trying to tell google that if someone goes to my product not found page to de-index that url it came from. I try this but get an e error...

     rs.Close();
               Response.StatusCode = 410;
				Response.End();
return;

Code (markup):

any ideas?

 

Better put a no index, no follow in your 404 page.