public Task <VMInvitation> ReadAsync(string code)
        {
            var data = DbContext.InvitationCodes
                       .Where(m => m.Id == code)
                       .Select(VMInvitation.Read(DbContext))
                       .ToList()
                       .SingleOrDefault();

            return(Task.FromResult(data));
        }
        public Task <VMInvitationIndex> IndexAsync()
        {
            var invitations = DbContext.InvitationCodes
                              .Select(VMInvitation.Read(DbContext))
                              .ToList();

            var data = new VMInvitationIndex
            {
                Invitations = invitations
            };

            return(Task.FromResult(data));
        }