Creating a "logged out" object

[Chumley the Walrus]

UPon a user succesfully logging in, i'm having trouble creating a "log
out" link on a protected page so that users can end their session (i'm
more used to classic asp with this). Below is my subroutine to check
for login, as i want to find a way to reverse " Session("ok") ="yes" "
for a log out object:

Sub dologin(Source as Object, E as EventArgs)
Dim strConn as string =
"SERVER=xxxxxxx;DATABASE=xxxxxx;UID=xxxx;PWD=xxxx; "
Dim MySQL as string = "Select name,password,usid from authusers " & _
"Where name = '" & lgname.text & "' and password = '" &
lgpassword.text & "'"
Dim MyConn as New SQLConnection(strConn)
Dim objDR as SQLDataReader
Dim Cmd as New SQLCommand(MySQL, MyConn)
MyConn.Open()
objDR=Cmd.ExecuteReader(system.data.CommandBehavio r.CloseConnection)

if Not objDR.Read() then
label1.text = "<i>Sorry - your user ID & password were not
found</i>"
objDR.Close
Myconn.Close
else
objDR.close
Myconn.Open
objDR=Cmd.ExecuteReader(system.data.CommandBehavio r.CloseConnection)
Session("ok") ="yes"
response.redirect("protectedpage.aspx")

End If
End Sub