var query = formscontext.GetATClientsERCWithAllInformationQuery(guid);
        try
        {
            LoadOperation<ATClient> _loadReturnTypeOperation = formscontext.Load(query);
            _loadReturnTypeOperation.Completed += (s, e) =>
            {
            some code goes here
            }

[Query(HasSideEffects=true)]
    public IQueryable<ATClient> GetATClientsERCWithAllInformation(List<Guid> clientsGuids)
    {
        return this.ObjectContext.ATClients.Include("ClientEfileInfo").Include("ATClientImages").Include("ATPreparer").Include("ATPreparer.ATFirm").Include("ATClientReturns")
            .Include("ATClientReturns.ATForms").Include("ATClientReturns.ATForms.FormsMaster").Where(p => clientsGuids.Contains(p.ClientGUID));
    }

protected override void OnError(DomainServiceErrorInfo errorInfo)