c# - The name 'HttpUtility' does not exist in the current context (winform) -

iget following error:

the name 'httputility' not exist in current context

i building winform app code using framework 4 client profile , can't find system.web reference:

string longurl = "https://test.com/currentaccount/pages/current.aspx";                         var uribuilder = new uribuilder(longurl);                         var query = httputility.parsequerystring(uribuilder.query);//error                         query["ltfrom"] = fromdate;                         query["ltto"] = todate;                         query["ltfilterselected"] = "none";                         uribuilder.query = query.tostring();                         longurl = uribuilder.tostring(); 

what problem?

httputility cannot accepted clientprofile - change .net version full.