Question : In .net, how can i write a userID and password validation method using linq?

Please fix in the following method.  Appreciate the help.  The error I receive is below:

Private Function isValidLogin(ByVal userID as String, ByVal pwd as String) as Boolean
        '=== Here is what I have and what I need:
        '==========================================================================
        '=== 1. Binary Encrypt pwd (already have a method for that)
        '=== 2. Use linq to obtain the ORI if login credentials are valid.
        '==========================================================================
        Dim db As New TransactionDataDataContext
        Dim binaryPassword As System.Data.SqlTypes.SqlBinary = BinaryCrypto.BinaryEncrypt(pwd)

        Try
            Dim loggedin = From Login In db.UserTables
                Where Login.Username.ToLower = userID.ToLower And Login.Password = BinaryPassword
                Select Login.ORI

            If loggedin.Count > 0 Then Return loggedin.ToList(0)
        Catch ex As Exception
            msg = "An error occured while logging in: " & ex.ToString
            Return Nothing
        Finally
            db = Nothing
        End Try

        msg = "The login credentials entered are incorrect.  Please try again."
        Return Nothing

End Function

NOTE:  The database column 'Password' is a varbinary Type.
Error:
Overload resolution failed because no accessible '=' can be called with these arguments:
    'Public Shared Operator =(x As System.Data.SqlTypes.SqlBinary, y As System.Data.SqlTypes.SqlBinary) As System.Data.SqlTypes.SqlBoolean': Value of type 'System.Data.Linq.Binary' cannot be converted to 'System.Data.SqlTypes.SqlBinary'.
    'Public Shared Operator =(binary1 As System.Data.Linq.Binary, binary2 As System.Data.Linq.Binary) As Boolean': Value of type 'System.Data.SqlTypes.SqlBinary' cannot be converted to 'System.Data.Linq.Binary'.

Answer : In .net, how can i write a userID and password validation method using linq?

Check the following
http://msexchangeteam.com/archive/2007/02/19/435472.aspx
http://technet.microsoft.com/en-us/library/bb851505(EXCHG.80).aspx