/// <summary>
        /// finds a list of users by their wallet.
        /// </summary>
        /// <param name="wallet"></param>
        /// <param name="where"></param>
        /// <returns>List<CustomUser></returns>
        public List <CustomUser> FindByWallet(double wallet, string where)
        {
            List <CustomUser> result;

            switch (where)
            {
            case "Equal":
                result = db_user.FindUserByWallet(wallet);
                break;

            case "Higher":
                result = db_user.FindUserByWalletHigher(wallet);
                break;

            case "Lower":
                result = db_user.FindUserByWalletLower(wallet);
                break;

            default:
                result = new List <CustomUser>();
                break;
            }

            return(result);
        }