Clear query string error Collection is read-only in ASP.Net

I need to clear the queryString so I implemented an httpmodule

public void Init(HttpApplication context) { context.PostRequestHandlerExecute += newEventHandler(OnEndRequest); }

and this is the method :

public void OnEndRequest(Object sender, EventArgs e) { HttpApplication context = (HttpApplication)sender; if (HttpContext.Current.Request.QueryString != null && HttpContext.Current.Request.QueryString.Count != 0) { HttpContext.Current.Request.QueryString.Clear(); } } but it's giving an exception :

System.NotSupportedException was unhandled by user code HResult=-2146233067 Message=Collection is read-only.