How to redirect to an .aspx page from a non-web project?

Hi,
I'm working on a asp.net application, the overall solution has 11 project under it. I have:
Project A - does not have a web interface, it is a library, with various functions;
Project B - does have a web interface, has web forms pages.
From a function in Project A, I need to go to an .aspx page in Project B, and pass 3 parameters.
I have tried this code:
string path = "http://...../Common/MyPage.aspx?cid=" + c+ "&oid=" + o + "&pid=" + p; HttpContext.Current.Response.Redirect(path);
But it threw an exception:
Object reference not set to an instance of an object.
If I use "Server.Transfer", instead of Response.Redirect, will it work?
I searched around but did not find a solution.
Anyone has a suggestion?
Thanks,
Claudia