UserDataAccess.cs

        public List<UserEntity> GetAllUsers(){

            SqlConnection oCon = null;
            SqlCommand oCmd = null;
            List<UserEntity> Users = null;
            SqlDataReader dr;

            try
            {
                oCon = _connection.openConn();
                string sql = string.Format("SELECT * FROM Users");
                oCmd.CommandText = sql;
                dr = oCmd.ExecuteReader();

                if (dr.HasRows)
                {
                    Users = new List<UserEntity>();

                    while (dr.Read())
                    {
                        UserEntity user = new UserEntity();
                        user.email = dr["email"].ToString();
                        user.password = dr["password"].ToString();
                        user.username = dr["username"].ToString();
                        user.usr_Id = Convert.ToInt32(dr["usr_Id"]);
                        Users.Add(user);
                    }
                }
            }
            catch (Exception ex)
            {
                throw ex;
            }

            return Users;
        }