LINQ Restrictions with CRM 2011 xRM Provider

Apparently there are different rules with the LINQ provider in the CRM 2011 SDK from the CRM 4.0 LINQ provider, and I ran into one today.

I have a process were I am deleting old email activities that meet a specific criteria in the subject line.  I had a LINQ query in CRM 4.0 console app that worked just fine:


var Emails = (
 from e1 in xrmConnection.EmailSet
 join i in xrmConnection.IncidentSet on e1.RegardingObjectId.Id equals i.IncidentId
 where e1.CreatedOn.Value <= dt
 && e1.Subject.ToString().StartsWith("XYZ:", true, null) 
 where i.IncidentStageCode.Value == 200999 && i.Custom_ResolvedOn.Value <= dt
 select e1).Take(MaxRecordsToProcess).ToList();

When I ran this same LINQ query in CRM 2011, it didn't work and threw this error:

Invalid 'where' condition. An entity member is invoking an invalid property or method.


After a search, I found this forum post that explained the error and after trial and error I found my specific problem.  The key point is this forum post is this limitation statement:
A limitation of the CRM LINQ provider is that:


    1.The left hand side of a predicate (where clause) MUST be an entity attribute 
    2.The right hand side of a predicate MUST be a literal value or variable 



At first, I didn't see it because I was putting them in the right order...the problem was the the string check didn't actually compare it to 'true'.

var Emails = (
 from e1 in xrmConnection.EmailSet
 join i in xrmConnection.IncidentSet on e1.RegardingObjectId.Id equals i.IncidentId
 where e1.CreatedOn.Value <= dt
 && e1.Subject.ToString().StartsWith( "XYZ:" , true, null) == true
 where i.IncidentStageCode.Value == 200999 && i.Custom_ResolvedOn.Value <= dt
 select e1).Take(MaxRecordsToProcess).ToList();


Adding that '== true' to the string comparison solved it.   

Weird.