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Using two different data context in a LINQ JOIN Query

I went through the many questions that were asked regarding this and tried to find solution but no luck. So here is my situation:
private IQueryable<tblB> MT;
var IDs = (from z in db1.tblA
where z.TA == User.Identity.Name
select z).ToArray();
MT = from s in db2.tblB
join a in IDs on s.BP equals a.BP
select new tblB() { LastName = s.LastName});
return View(MT.ToPagedList(pageNumber, pageSize));
I'm getting exception at the return statement - $exception {"Unable to create a constant value of type 'tblA'. Only primitive types or enumeration types are supported in this context."} System.NotSupportedException
When I debug IDs array, I see it has data from tblA but 2nd query with join doesn't seem to work. What mistake am I making. Help!!!

You need to use Contains in order to generate and IN sql clause:
First, change the first query to return the primitive data you need:
var IDs = (from z in db1.tblA
where z.TA == User.Identity.Name
select z.BP).ToArray();
Then use that in-memory list in the second query:
MT = from s in db2.tblB
where IDs.Contains(s.BP)
select new tblB() { LastName = s.LastName});
By the way, this is not a 2 contexts operations. You're loading data from the first context into memory (notice the .ToArray()) and then using these in-memory data to query the second context.

So you want as a result all elements of tblB that have a property BP equal to at least one of the BP properties of the elements in IDs.
The problem is that after ToList() IDs is in local memory, while your db1.tblB is on the database. You have to bring both sequences to the same platform, either both to your database, or both to local memory. Whatever is more efficient depends on the actual sizes of the sequences and of the results
Use Contains if you want to perform the query on database side. The complete list of IDs will be transferred to the database, where the query will be executed and the results will be transferred to local memory.
Use this method if IDs is fairly short and your result is not almost the complete tblA
var result = db2.tblB
.Where(elementOfTableB => IDs.Contains(elementOftableB);
No need to create a new tblB object, apparently you want the complete tblB object.
Use AsEnumerable if you expect that there are a lot of IDs in comparison to the number of element in tblB. Transferring the IDs to the database would take considerably more time than transferring the complete tblB to local memory.
db2.TblB // take all tblBelements
.AsEnumerable() // bring to local memory
.join(IDs, // join with list IDs
tblBElement => tblBElement.BP // take from each tblBElement the BP
idElement => idElement.BP // take from each ID the BP
(tblBElement, idElement) => // when they match take the two records
// and get what you want.
tblBElement); // in this case the complete tblBElement

Linq Join when second table will have multiple records

Trying to create a Linq query that can do multiple searches in one command instead of having multiple search result pages. It is working great when I am trying to find multiple records that have a subject (in my case CHIEF_COMPLAINT) and comments with a specific word. The problem is when I want to search with serial numbers.
There are two issues here. One is that multiple pieces of equipment can be attached to a specific ticket and also a single piece of equipment can be associated with multiple tickets. When I query the table used to associate equipment to tickets (VIEW_WT_EQUIP, using the view because it is where the serial number is seen) I potential get multiple results with the same Ticket_ID.
This is the query that I have right now, but it returns no results when I put in a serial number that I know is in the system.
var query = from a in db.VIEW_WT_HEADERs
join c in db.VIEW_WT_EQUIPs on a.TICKET_ID equals c.TICKET_NUMBER into c_group
from c2 in c_group
join b in db.WT_EVENTs on a.TICKET_ID equals b.TICKET_ID
where b.COMMENTS.Contains(input) || a.CHIEF_COMPLAINT.Contains(input) || c2.SERIAL_NUMBER.Contains(input)
orderby a.TICKET_ID descending
select new { a.TICKET_ID, a.ENTRY_DATE, a.CONTACT, a.CHIEF_COMPLAINT, a.STATUS };
I also tried a method where I used 2 linq queries and put all the ticket numbers from a serial number search into a list, but the second query didn't like that I was trying to compare an int array.
I think I am just going about this wrong. Join is probably not the right way to do this, but I don't know how to tell the main query to pull all the tickets associated with a piece of equipment.
Please let me know where I can clarify, because I know this explination is rough.

I would put this as comment instead of an answer, but I want to show you some code, so I had to choose "answer".
If you are using Linq to Entities, you probably have a relationship between the objects. It means that the join is not necessary. You should only use join when no navigation property is available.
I can't tell exactly what you should do, but here is some code the might be helpful:
var query = from a in db.VIEW_WT_HEADERs
from b in a.WT_EVENTs
from c in a.VIEW_WT_EQUIPs
where b.COMMENTS.Contains(input) || a.CHIEF_COMPLAINT.Contains(input) ...
orderby a.TICKET_ID descending
select new { a.TICKET_ID, a.ENTRY_DATE, a.CONTACT, a.CHIEF_COMPLAINT, a.STATUS };
you can also use let to store a sub-expression:
var query = from a in db.VIEW_WT_HEADERs
from b in a.WT_EVENTs
from c in a.VIEW_WT_EQUIPs
let x = c.FirstOrDefault()
where b.COMMENTS.Contains(input) || a.CHIEF_COMPLAINT.Contains(input) || x.SomeProperty ....
orderby a.TICKET_ID descending
select new { a.TICKET_ID, a.ENTRY_DATE, a.CONTACT, a.CHIEF_COMPLAINT, a.STATUS };
Those are just example, maybe it helps!

Join data from IQueryable and IList<KeyValuePair>

I'm trying to join a row of parent data to a related collection which has been squeezed into a single piece of data.
I have an IQueryable of Orders:
IQueryable<Order> orderList = context.Set<Order>
.Where("OrderDate >= #0", startDate)
.Where("OrderDate <= #0", endDate)
and a related IList<KeyValuePair<int, string>> where each KVP contains the OrderID and a concatenated string of the product names from each Order Line. I want to join the Value from the correct KeyValuePair to the Order info based on the OrderID Key.
To illustrate, the desired output would look something like:
OrderNum OrderDate Customer State OrderTotal Products_Ordered
12345 12/12/2012 J.Bloggs WA $25.50 Bolts, Hammer, Suregrip Clamp
I am trying a linq join that looks like this:
IQueryable result = from o in orders
join line in orderLines on o.OrderID equals line.Key
select new
{
o.OrderNum
o.OrderDate,
o.Customer.CustomerFullName,
o.DeliverAddress.State,
o.TotalPrice,
line.Value
}
The method performing the join seems to work, but when I access the returned IQueryable, I get a NotSupportedException: Unable to create a constant value of type 'System.Collections.Generic.KeyValuePair`2'. Only primitive types or enumeration types are supported in this context.
What am I doing wrong?

Your IQueryable is actually a specialized entity framework implementation that, when iterated, attempts to construct an SQL query by examining an expression tree, execute this query, and return an enumerable over the results. This is fragile, and your projections and queries can't be arbitrarily complex, or the expression -> SQL converter has no idea what to do with it.
Fixing this by materializing your IQueryable first is fine, but you don't even really need to do that. Why have a list of what is essentially tuples, when what you want is a dictionary that maps the order ID to a bunch of data?
IDictionary<int, string> orderLines = new Dictionary<int, string>();
// Add a dummy item
orderLines[1234] = "Hello, this, is, a, test";
// Get your combined view
// Assuming you have an order with 1234 as the ID, this should work
var result = from o in orders
select new
{
o.OrderNum
o.OrderDate,
o.Customer.CustomerFullName,
o.DeliverAddress.State,
o.TotalPrice,
Products = orderLines[o.OrderID]
}

Entity Framework has issues with some types, because it tries to push them to the backing database. The quick and easy solution is to pull the data down before performing the join.
var orderList = context.Set<Order>
.Where("OrderDate >= #0", startDate)
.Where("OrderDate <= #0", endDate)
.ToList(); // ------> Relevant line <------
var result = from o in orderList
join line in orderLines on o.OrderID equals line.Key
select new
{
o.OrderNum
o.OrderDate,
o.Customer.CustomerFullName,
o.DeliverAddress.State,
o.TotalPrice,
line.Value
};
It's just a change in where the joining happens, RDBMS- or client-side.
Performance won't be an issue, assuming you don't have a ton of data and all rows will be matched. Of course, you will have to pull down data that doesn't get joined, so if only a few of orderList will be in result, that might be worth a second thought, design-wise. The only alternative would be in pushing the KeyValuePair items to the server first, which probably isn't what you're looking for.

Joining a query result (IQueryable) with a normal enumerable stored in memory (IEnumerable<...>) doesn't make much sense. Think about it, the query doesn't get processed until it's materialized, injecting your own data in queries is done in the query text itself -- that's not what you really want, now is it?
I think what you expect from this is best achieved by first materializing the IQueryable into an IEnumerable<>, then doing a plain LINQ join on two IEnumerable<>s, which is trivial.
It's not like you'd be using the IEnumerable<> to filter the result set on the server side, you're not really losing any performance here.
Edit: Note that if you are using the IEnumerable<> to filter the results on the server side, you can do that! EF (I assume that's what you're using) has very strong special cases for things like IQueriable<>.Any<>() with an IEnumerable<>.Contains<>() inside it -- it inserts the literal values in the query text. It's just the actual join that doesn't make much sense in this context.

Getting only specific columns in entity framework lambda join

I am surprised I cannot find a solution for this on the web, but wording the search terms was a bit difficult. The question I have is about generating entity SQL that only returns the needed columns in a group join using Lambda syntax.
The following is a "toy" example. I am not joining on two entities, rather on an enumerated list and an entity. And tunnelling is not an acceptable answer. I need to apply this to a much larger problem using a group join and select many.
var result1 = clientprofiles.Join(Context.Adjusters,
c => c.AdjusterId,
a => a.AdjusterId,
(c, a) => new {a.ClientAccountId}).ToList();
Using Julie Lehrman's Entity profiler, I see that the query is being generated to select every record in the rows that meet the join criteria. How do I pare it down so it only selects the ClientAccountId field in this example?

You can project a set of columns on any select from the context, so in your case you can constrain the Context.Adjusters parameter by using
Context.Adjusters.Select(a=> new { a.ClientAccountId })
to constrain the query to just the single column

Joining a Many to Many table

I have a situation where I am providing a method to query for data in various ways. We provide the user with 4 different fitler criteria and they can mix and match as much as they want.
For example:
public Fruit GetFruit(Boolean isLocal, string storeName, string classificationType, string state);
This is simple when all of the attributes are on the table, but my issue arises as a result of complexity in the data model. Three of my attributes are simple, they are just joins, but i have one table that sits behind a one to many relationship. So in order to query for it I have to do a many to many join.
So lets say i am trying to determine all fruit a store offers. A store has a list of fruits and our classificationType sits behind a many relationship (FruitClassification)
alt text http://tinyurl.com/39q6ruj
The only successful way i have been able to query this in EF is by selecting all Fruits (by classification), and then selecting all stores that meet the filter criteria and then joining them.
You would think this query in ef would be functional:
var final = (
from s in Stores
join fc in FruitClassifications.Where(z=>z.Classifications.Code == classificationType && z.Classifications.Type.Code =="FRT").Select(x=>x.Fruit).Distinct()
on s.Fruits.Id equals f.Id
where s.Name=name && s.isLocal && s.State==state
select s
).ToList();
But it runs horrible(and looks the same when i profile it), Is there any way i can push this query down to the database? A better way to query?

I think this is what you want:
var final = (from s in Stores
where s.Name=name && s.isLocal && s.State==state
&& s.Fruits.Any(f =>
f.FruitClassifications.Any(fc => fc.Code == classificationType
&& fc.Type.Code == "FRT"))
select s).ToList();

http://learnentityframework.com/LearnEntityFramework/tutorials/many-to-many-relationships-in-the-entity-data-model/
this might help you. EF has the possibility to generate those relations with navigation properties from the designer, so you don't have to use the join.