public bool LogearseFirebird(string Cif, string PWD)
    {
        bool oReturn = false;
        string connString =
                    "User=SYSDBA;" +
                    "Password=masterkey;" +
                    "Database=C:\FirebirdDB\USUARIOS.FDB;" +
                    "DataSource =localhost;" +
                    "Port=3050;" +
                    "Dialect=3;" +
                    "Charset=NONE;" +
                    "Role=;" +
                    "Connection lifetime=15;" +
                    "Pooling=true;" +
                    "MinPoolSize=0;" +
                    "MaxPoolSize=50;" +
                    "Packet Size=8192;" +
                    "ServerType=0;";


        FbConnection conn = new FbConnection(connString);
        conn.Open();

        String sql = "SELECT NOMBRE FROM TBL_USUARIOS WHERE CIF=" + Cif + "AND CONTRASENYA=" + PWD;
        FbCommand com = new FbCommand(sql, conn);
        FbDataReader dr = com.ExecuteReader();
        if (dr.Read())
        {
            oReturn = true;
        }
        dr.Close();
        conn.Close();
        Console.ReadLine();
        return oReturn;
    }
}