How to attach sqlite Unencrypted database to an encrypted one

Please need a help...i want to attach an unencrypted sqlite database to another encrypted one, I am using DevExpress XpoDefault.Session to do that..but I always get error message "File is encrypter or not a database".

string conStr = string.Format( "XpoProvider=SQLite;Data Source={0};Password=1234", MyEncryptedDbFile );

MyDatalayer = XpoDefault.GetDataLayer(conStr, AutoCreateOption.DatabaseAndSchema);

string s = Path.Combine(Application.StartupPath, MyUnEncryptedDbFile);
XpoDefault.Session = new UnitOfWork(MyDataLayer);
string st = string.Format("attach database '{0}' as AttachedAlias", s);
XpoDefault.Session.ExecuteNonQuery(st); /// Error File is encrypted or not database.....*

Best regards, and excuse my english