Question

For some reason in my where it says that “firstname” does not exist in the Opportunity Entity. But it is set for the SystemUser Entity. Any idea why it is getting confused? Thanks!

            var linqQuery = (from r in gServiceContext.CreateQuery("opportunity")
                             join c in gServiceContext.CreateQuery("account") on ((EntityReference)r["accountid"]).Id equals c["accountid"]
                             join u in gServiceContext.CreateQuery("systemuser") on ((EntityReference)r["ownerid"]).Id equals u["systemuserid"]
                             where r["new_leadstatus"].Equals("100000004") && u["lastname"].Equals(rsmLastName) && u["firstname"].Equals(rsmFirstName)
                             select new
                             {
                                 AccountId = !r.Contains("accountid") ? string.Empty : r["accountid"],
                                 Account = !r.Contains("name") ? string.Empty : r["name"]
                             });

Answer 1

Make sure you put each where clause in its own line per Microsoft guidelines.

The where clause applies a filter to the results, often using a
Boolean expression. The filter specifies which elements to exclude
from the source sequence. Each where clause can only contain
conditions against a single entity type. A composite condition
involving multiple entities is not valid. Instead, each entity should
be filtered in separate where clauses.

var linqQuery = from r in gServiceContext.CreateQuery("opportunity")
                join c in gServiceContext.CreateQuery("account") on ((EntityReference)r["accountid"]).Id equals c["accountid"]
                join u in gServiceContext.CreateQuery("systemuser") on ((EntityReference)r["ownerid"]).Id equals u["systemuserid"]
                where r["new_leadstatus"].Equals("100000004")
                where u["lastname"].Equals(rsmLastName) && u["firstname"].Equals(rsmFirstName)
                select new
                {
                    AccountId = !r.Contains("accountid") ? string.Empty : r["accountid"],
                    Account = !r.Contains("name") ? string.Empty : r["name"]
                };