Compiler Error Message: BC30002: Type 'LdapAuthentication' is not defined

[Nuve]

I followed the instructions on the Microsoft article
(http://support.microsoft.com/default.aspx?scid=kb;en-
us;326340) on HOW TO: Authenticate against the Active
Directory by Using Forms Authentication and Visual
Basic .NET. After completing and running the page I get
the following error message on the Logon.aspx file:

Compiler Error Message: BC30002: Type 'LdapAuthentication'
is not defined.

Source Error:
Line 19: sub Login_Click(sender as object,e as EventArgs)
Line 20: Dim adPath as String
= "LDAP://DC=dec,DC=com" 'Path to your LDAP directory
server
Line 21: Dim adAuth as LdapAuthentication = new
LdapAuthentication(adPath)
Line 22: try
Line 23: if(true = adAuth.IsAuthenticated
(txtDomain.Text, txtUsername.Text, txtPassword.Text)) then
Anyone have any idea of how to fix this?
Thanks
nuve