Hello My Friends,

I have reached a way to resolve my problem. I am attaching the source code 
of Global.asax that access an XML file whoisonline.xml and store the 
online poeple as :
<?xml version="1.0" standalone="yes"?>
<whoisonline>
  <profile>
    <id>1</id>
    <headline>Text Here</headline>
  </profile>
</whoisonline>

Global.asax

Sub Session_End()

If Context.Request.IsAuthenticated Then
 Application( "SessionCount" ) -= 1
 Dim myDateSet = New DataSet()
 myDateSet.ReadXml("M:\database\whoisonline.xml")
 Dim myTable As DataTable = myDateSet.Tables("profile")
 Dim id as string = Cstr(Context.User.Identity.Name)
 Dim myDatarow as DataRow
 For Each myDatarow in myTable.Rows
	If myDatarow(0).ToString() = Id then 
		myDatarow(0).Delete()
		Exit For
	End If
 Next
 myDateSet.WriteXml("M:\database\whoisonline.xml")
 
End If
End Sub

Sub Application_AuthenticateRequest(ByVal sender As Object, ByVal e As 
EventArgs)
If Context.Request.IsAuthenticated Then
If Application( "SessionCount" ) Is Nothing Then
    Application( "SessionCount" ) = 0
End If
Application( "SessionCount" ) += 1
Dim myDateSet = New DataSet()
myDateSet.Readxml("M:\database\whoisonline.xml")
Dim myTable As DataTable = myDateSet.Tables("profile")
Dim strExpr as String
strExpr = "id = " & Context.User.Identity.Name
Dim foundRows() As DataRow
foundRows = myTable.Select(strExpr)
If foundRows.GetUpperBound(0) < 0 then
    Dim myRow As DataRow 
    myRow = myTable.NewRow()
    myRow("id") = Context.User.Identity.Name
	  Dim objFormsID As FormsIdentity
	  objFormsID = Context.User.Identity
    myRow("headline") = objFormsID.Ticket.UserData
    myTable.Rows.Add(myRow)
End If
 myDateSet.WriteXml("M:\database\whoisonline.xml")
End If
End Sub

I have tried to store them as array in Application, but it was not much  
reliable. So i thought of storing it in XML file. Do you think it is 
better to store them as XML? or SQLServer Table? Is there any suggestions 
for enhancing the above coding? thank you in advance...
Rabih