Not able to retrieve session variable

I'm trying to access the session variable in my business logic area.  My aspx page calls a function in the following manner:
<%
#BusinessLogic.WebSite.GetSiteImage(Container.DataItem("WebSiteID"), 111, 82, "images")%>
Public Shared Function GetSiteImage(ByVal siteid As Integer, Optional ByVal width As Integer = 111, Optional ByVal height As Integer = 82, Optional ByVal pathOfImageFolder As String = "images") As String Dim Cat As String = HttpContext.Current.Session("Cat") & "link exchange" 'HttpContext.Cur ...