Question

I have a linq query that I need to have doing left joins instead of inner joins. All of the examples I see show only 1 left join but when I tried it with 2 i couldn’t get it right. So how would this change to use 2 left joins?

ruleSets = (from rs in db.RuleSets
                    join brs in db.BatchRuleSets on rs.ID equals brs.RuleSetID
                    join b in db.Batches on brs.BatchID equals b.id
                    where !clientId.HasValue || b.ClientID == clientId.Value
                    where !batchId.HasValue || brs.BatchID == batchId.Value
                    select new
                    {
                        rs.ID,
                        rs.Description,
                        rs.IsActive,
                        rs.CreatedDate,
                        rs.EffectiveDate,
                        rs.ExpirationDate,
                        BatchName = b.FileName,
                        b.ClientID
                    }).ToList().Select(x => new { 
                        x.ID,
                        x.Description,
                        x.IsActive,
                        x.CreatedDate,
                        x.EffectiveDate,
                        x.ExpirationDate,
                        x.BatchName,
                        ClientName = GetClientName(x.ClientID)});

Answer 1

    ruleSets = (from rs in db.RuleSets
                join brs in db.BatchRuleSets on rs.ID equals brs.RuleSetID into j1

                from jbrs in j1.DefaultIfEmpty()
                join b in db.Batches on jbrs.BatchID equals b.id into j2

                from jb in j2.DefaultIfEmpty()
                where !clientId.HasValue || jb.ClientID == clientId.Value
                where !batchId.HasValue || jbrs.BatchID == batchId.Value
                select new
                {
                    rs.ID,
                    rs.Description,
                    rs.IsActive,
                    rs.CreatedDate,
                    rs.EffectiveDate,
                    rs.ExpirationDate,
                    BatchName = jb.FileName,
                    jb.ClientID
                }).ToList().Select(x => new { 
                    x.ID,
                    x.Description,
                    x.IsActive,
                    x.CreatedDate,
                    x.EffectiveDate,
                    x.ExpirationDate,
                    x.BatchName,
                    ClientName = GetClientName(x.ClientID)});