I have list A that has a lookup to list B that allows multiple entries. One A to multiple related Bs - standard practice. I want to find A where B contains a reference to a particular instance of 'b'.
I've tried:
var As = from a in ARecs where a.Bs.Contains(b) select a;
But I get the usual 'multiple tables involved' error. How do I go about this please?
thanks in advance
the error I'm getting is "The query uses unsupported elements, such as references to more than one list, or the projection of a complete entity by using EntityRef/EntitySet."
The A and B list code is generated by SPMetal if that makes any difference
Some LINQ cannot be turned into CAML (did I forget to mention this was on SPMetal generated LINQ to Sharepoint - doh!) and needs to be performed as 2 queries - the first ToList then the 2nd on that list. This worked for me.
Var Bs = A.ToList().Where(record => record.Bs.Contains(b))
Related
I'm trying to get a list of cases whose AccountID is found in a previous list.
The error occurs on the last line of the following:
// Gets the list of permissions for the current contact
var perms = ServiceContext.GetCaseAccessByContact(Contact).Cast<Adx_caseaccess>();
// Get the list of account IDs from the permissions list
var customerIDs = perms.Select(p => p.adx_accountid).Distinct();
// Get the list of cases that belong to any account whose ID is in the `customerID` list
var openCases = (from c in ServiceContext.IncidentSet where customerIDs.Contains(c.AccountId) select c).ToList();
I'm not sure what the "invalid property" is the error is talking about. The code compiles, I just get the error at runtime.
The problem is the CRM Linq Provider. It doesn't support all of the available options that the Linq-to-objects provider offers. In this case, the CRM does not support the Enumerable.Contains() method.
where:
The left side of the clause must be an attribute name and the
right side of the clause must be a value. You cannot set the left side
to a constant. Both the sides of the clause cannot be constants.
Supports the String functions Contains, StartsWith, EndsWith, and
Equals.
You can work around this in one of two ways:
Rework your query to use a more natural join.
If a join is not possible, you can use Dynamic Linq to generate a list of OR clauses on each item in customerIDs. This would function similarly to Enumerable.Contains.
See my answer or the accepted answer to the question "How to get all the birthdays of today?" for two separate ways to accomplish this.
I have a simple LINQ EF query below using the method syntax. I'm using my Include statement to join four tables: Event and Doc are the two main tables, EventDoc is a many-to-many link table, and DocUsage is a lookup table.
My challenge is that I'd like to shape my results by only selecting specific columns from each of the four tables. But, the compiler is giving a compiler is giving me the following error:
'System.Data.Objects.DataClasses.EntityCollection does not contain a definition for "Doc' and no extension method 'Doc' accepting a first argument of type 'System.Data.Objects.DataClasses.EntityCollection' could be found.
I'm sure this is something easy but I'm not figuring it out. I haven't been able to find an example of someone using the multi-table include but also shaping the projection.
Thx,Mark
var qry= context.Event
.Include("EventDoc.Doc.DocUsage")
.Select(n => new
{
n.EventDate,
n.EventDoc.Doc.Filename, //<=COMPILER ERROR HERE
n.EventDoc.Doc.DocUsage.Usage
})
.ToList();
EventDoc ed;
Doc d = ed.Doc; //<=NO COMPILER ERROR SO I KNOW MY MODEL'S CORRECT
DocUsage du = d.DocUsage;
Very difficult to know what is going on without a screencap of your model, including the navigational properties on each entity.
But if your saying it's a many-to-many between Event and Doc (with EventDoc being the join table), and assuming your join table has nothing but the FK's and therefore doesn't need to be mapped, then shouldn't a single Event have many Doc's?
This query:
var query = ctx.Event.Include("EventDoc.Doc");
Would imply (based on the lack of pluralization): a single Event has a single EventDoc which has a single Doc.
But shouldn't that be: a single Event has a single EventDoc which has many Doc's.
Therefore your projection doesn't really make sense. Your trying to project to an anonymous type, with EventDate and Filename for a single Doc, but an Event has many Docs.
Maybe a projection like this would be more suitable:
var query = ctx.Event.Include("EventDoc.Docs.DocUsage")
.Select(x => new
{
EventDate = x.EventDate,
DocsForEvent = x.EventDocs.Docs
}).ToList();
And for that you work you need to fix up your model. Im surprised it even validates/compiles.
Either your model is wrong or your description of the database cardinalities in your question is. :)
Of course, i could be completely misunderstanding your database and/or model - so if i am let me know and i'll remove this answer.
I'm building a poll widget. I've 2 tables, call them Polls and PollsCompleted. I need to do a linq query to get all the Polls that do not exist for a given user in PollsCompleted.
I have the following sets:
For Polls
Where Active == True
For PollsCompleted
Where UserId == ThisUserId
Where PollId = Polls.Id
Now I need to get all Polls that do not exist in PollsCompleted. I need an example for this using either a single or multiple queries. I've tried to break it down into 2 queries.
Basically, I've 2 IQueryables of type T and T1. I want to take all T's where T.ID does not exist in T1.ParentId.
T.Where(x => ! T1.Select(y => y.ParentID).Contains(x.ID))
In Linq you often work from the bottom up. Here we first get a collection of all the parentIDs in T1 -- the T1.Select(...) part. Then we create a where clause that selects all of the Ts whose IDs are not contained in that set.
Note that the result is a query. To materialize it, use ToList() or similar on the statement above.
Use Except. That will work in this case.
For your reference Enumerable.Except Method
I have a List and each Filter object has a property called "Id". I want to fetch all the records from my database using Linq to SQL that contains those ids. The List is not part of the database it is just an independent list.
not very clear question. however this is what, i suppose, u r trying to do
from c in datacontext.TableName where
IndependentList.Contains(c=>c.id)
select c
So I'm extremely new to Linq in .Net 3.5 and have a question. I use to use a custom class that would handle the following results from a store procedure:
Set 1: ID Name Age
Set 2: ID Address City
Set 3: ID Product Price
With my custom class, I would have received back from the database a single DataSet with 3 DataTables inside of it with columns based on what was returned from the DB.
My question is how to I achive this with LINQ? I'm going to need to hit the database 1 time and return multiple sets with different types of data in it.
Also, how would I use LINQ to return a dynamic amount of sets depending on the parameters (could get 1 set back, could get N amount back)?
I've looked at this article, but didn't find anything explaining multiple sets (just a single set that could be dynamic or a single scalar value and a single set).
Any articles/comments will help.
Thanks
I believe this is what you're looking for
Linq to SQL Stored Procedures with Multiple Results - IMultipleResults
I'm not very familiar with LINQ myself but here is MSDN's site on LINQ Samples that might be able to help you out.
EDIT: I apologize, I somehow missed the title where you mentioned you wanted help using LINQ with Stored Procedures, my below answer does not address that at all and unfortunately I haven't had the need to use sprocs with LINQ so I'm unsure if my below answer will help.
LINQ to SQL is able hydrate multiple sets of data into a object graph while hitting the database once. However, I don't think LINQ is going to achieve what you ultimately want -- which as far as I can tell is a completely dynamic set of data that is defined outside of the query itself. Perhaps I am misunderstanding the question, maybe it would help if you provide some sample code that your existing application is using?
Here is a quick example of how I could hydrate a anonymous type with a single database call, maybe it will help:
var query = from p in db.Products
select new
{
Product = p,
NumberOfOrders = p.Orders.Count(),
LastOrderDate = p.Orders.OrderByDescending().Take(1).Select(o => o.OrderDate),
Orders = p.Orders
};