CapDemo.BL.UserBL.ExistUser C# (CSharp) Метод

        public bool ExistUser(User User)
        {
            string query = "SELECT u.[User_ID],u.[Username],u.[Password]"
                        + " FROM [User] u";
            DataTable dt = DA.SelectDatabase(query);
            int i = 0;
            if (dt!= null)
            {
                foreach (DataRow item in dt.Rows)
                {
                    if (item["Username"].ToString().ToUpper() == User.UserName.ToUpper())
                    {
                        i++;
                    }
                }
            }
            if (i==0)
            {
                return false;
            }
            else
            {
                return true;
            }
        }