As the title suggests,
When and why would we use RetrieveMultipleRequest over Service.Retrievemultiple?
Can I please get one or two scenarios where one would be more preferable to the other?
My understanding is that RetrieveMultipleRequest is similar to doing a FetchXML query (and can in fact use FetchXML instead of a queryexpression).
Is this the reason? If so, what can you do in a FetchXML query you can't do in a QueryExpression?
According to the CRM 3.0 docs,
CrmService (IOrganizationService in CRM 2011) contains a set of methods common to many entities.
So the RetrieveMultiple method of the IOrganizationService interface is a shortcut method for the RetrieveMultipleRequest and RetrieveMultipleResponse action pairs. This is best seen when looking at the documentation for the RetriveMultipleRequest class on MSDN: the documented example references the IOrganizationService's RetrieveMultiple method, not the RetrieveMultipleRequest or the RetrieveMultipleResponse classes, which would also suggest Microsoft intends the two to be interchangeable.
Because they are interchangeable, you can pass FetchXml to the RetrieveMultiple method. See Anwar's answer to a similar question to see how and why you'd use FetchXml.
RetrieveMultiple method creates instance of RetrieveMultipleRequest class and sends it to server. No special purpose to use RetrieveMultipleClass directly.
Related
First off, this is related to Spring Data Rest: How to search by another object's key? which appears to be resolved in https://jira.spring.io/browse/DATAREST-502
My issue is (I believe) and extension of this. I'm seeing the following behavior:
I have two repository queries defined e.g.
Person findByAccount(#Param("account") Account account));
Collection<Person> findByAccountIn(#Param("accounts") Collection<Account> accounts));
Both search methods are exposed via spring-data-rest. I can access the first using a url such as http://localhost:8080/people/search/findByAccount?account=http://localhost:8080/accounts/1
I can access the second method using a url such as http://localhost:8080/people/search/findByAccountIn?accounts=http://localhost:8080/accounts/1, but if I try to pass in MULTIPLE accounts, such as
http://localhost:8080/people/search/findByAccountIn?accounts=http://localhost:8080/accounts/1,http://localhost:8080/accounts/2,
It will run the query except will IGNORE the first account (http://localhost:8080/accounts/1) and only search based on the second (http://localhost:8080/accounts/2)
What is the proper technique for passing in a Collection of entities to a repository argument over the REST API? I find it works great for a single entity, but not for a Collection. Note that both of these repository methods are working as expected when directly accessing the JpaRepository.
Also note that these queries seem to work if the collection is of some primitive type, for example findByAccountIdIn(#Param("accountIds") Collection<Long> accountIds) is accessible with intended functionality via http://localhost:8080/people/search/findByAccountIdIn?accountIds=1,2. This leads me to believe it's possibly an error in the way a list of URIs is passed into a query method which expects a Collection of corresponding entities.
Thanks in advance for any help!
Try repeat the query parameter as most servers will interpret this as a list. It might not be the prettiest solution but should work.
http://localhost:8080/people/search/findByAccountIn?accounts=http://localhost:8080/accounts/1&accounts=http://localhost:8080/accounts/2
I know that this is forever old, but I found the answer.
I will put this here for anyone else who should wander this way:
How to use List in endpoint exported by Spring Data REST?
List<Person> findByAccountIn(#Param("accounts") Account... accounts);
the request would look like this:
http://localhost:8080/people/search/findByAccountIn?accounts=http://localhost:8080/accounts/1&accounts=http://localhost:8080/accounts/2&accounts=http://localhost/accounts/anotheraccountid
I am looking for information about how to create dynamic queries using the newer StreamInsight 2.1 reactive extensions model. Specifically, I would like to use the CreatQuery() method or something similar (within IQueryable) with IQStreamable. Within the workflow I am creating, this new query would be inserted into StreamInsight as a standing query. I have done quite a bit of research but have not found a solution. Also, most of the documentation appears to reference what is now a "legacy" adapter model. Any help would be appreciated.
What do you mean by "Dynamic Query"? Something similar to Dynamic Query Composition, where you could use the output of one query as a stream input into another query? If that's the case, you can use Subjects for this. Subjects allow you to have multiple publishers/subscribers for a stream and also provide the ability to attach/detach publishers and subscribers at runtime.
As far as I remember StreamInsights does not support that concept, the only way to archive that would be to use dynamic compilation to publish to StreamInsights query instance compiled based on dynamically generated code. That is quite possible.
Within the context of C# on .Net 4.0, are there any built-in objects that implement IQueryable<T>?
IQueryable objects are produced by Queryable Providers (ex. LINQ to SQL, LINQ to Entities/Entity Framework, etc). Virtually nothing you can instantiate with new in the basic .NET Framework implements IQueryable.
IQueryable is an interface designed to be used to create Queryable providers, which allow the LINQ library to be leveraged against an external data store by building a parse-able expression tree. By nature, Queryables require a context - information regarding what exactly you're querying. Using new to create any IQueryable type, regardless of whether it's possible, doesn't get you very far.
That being said, any IEnumerable can be converted into an IQueryable by using the AsQueryable() extension method. This creates a superficially-similar, but functionally very different construct behind the scenes as when using LINQ methods against a plain IEnumerable object. This is probably the most plentiful source of queryables you have access to without setting up an actual IQueryable provider. This changeover is very useful for unit-testing LINQ-based algorithms as you don't need the actual data store, just a list of in-memory data that can imitate it.
Well, your question is kinda weird... but I believe that if you look at an interface in Reflector, it will give you a list of implementers in the loaded assemblies.
As a disclaimer I have not used Reflector since it went pay-for-play so I might be wrong.
EntityCollection does, as does EnumerableQuery.
Not that I think either of these is going to get you anywhere. To help, we need to know what you are really trying to solve. If you are writing a LINQ provider, you should read this: http://msdn.microsoft.com/en-us/library/bb546158.aspx.
They recommend writing your own implementation.
If you are looking for a way to instantiate an empty list of IQueryable, then you can use this:
IQueryable<MyEntity> = Enumerable.Empty<MyEntity>().AsQueryable()
I've been learning about IQueryable and lazy loading/deferred execution of queries.
Is it possible to expose this functionality over WCF? I'd like to expose a LINQ-to-SQL service that returns an IQueryable which I can then perform additional queries on at the client, and finally execute using a .ToList(). Is OData format applicable at all in this context?
If possible, what is the term for this technique and what are some good tutorials I can follow? Thank you.
You should check WCF Data Services which will allow you to define Linq query on the client. WCF Data Services are probably the only solution for your requirement.
IQueryable is still only interface and the functionality depends on the type implementing the interface. You can't directly expose Linq-To-Sql or Linq-To-Entities queries. There are multiple reasons like short living contexts or serialization which will execute the query so the client will get list of all objects instead of the query.
as far as i know, the datacontext is not serializable meaning that you cannot pass it around with WCF
You can use http://interlinq.codeplex.com/ which allows you to send Linq query over WCF.
WCF Data Services only can be using with webHttpBinding and not all Linq queries can be expressed. Writing queries when WCF Data Service is used is not so attractive - requires string expressions such as:
.AddQueryOption("$filter", "Id eq 100");
https://remotelinq.codeplex.com/ is another choice. But it works in AppDomain to scan the Current Assemblies and serialize them. This tech is not suitable to WinRT as no Domains for WinRT App
I've been struggling with the same question, and realized that a well formed question is a problem solved.
IQueryable basically serves to filter the query before sending it to your DB call so instead of getting 1000 records and filter only 10, you get those 10 to begin with. That filtering belongs to your Service Layer, but if you are building an API I would assume you would map it with AND/OR parameters in your URL.
http://{host}/{entity}/q?name=john&age=21.
So you end up with something like this:
Filter:Column1=Value1 > http://{host}/{entity}q?column1=value1 > SELECT *
FROM Entity
WHERE Column1=Value1
MVC > WCF > DB
You can find a very good sample [here]
Lastly, since your payload from the WCF will be most likely a JSON, you can (and should) then deserialize them in your Domain Models inside a collection. It is until this point where the paging should occur, so I would recommend some WCF caching (and since its HTTP, it's really simple). You still will be using LINQ on the WebApp side, just w/o "WHERE" LINQ clause (unless you want to dynamically create the URL expressed above?)
For a complex OR query, you mind end up with multiple WCF queries (1 per "AND") and then concatenate them all together
If it's possible to send IQuerable<> over WCF it's not a good thing security wise, since IQuerable<> could expose stuff like the connection string to the database.
Some of the previous comments seem promising though.
I understand that a IQueryable cannot be serialized. That means that queries can not be serialized, sent to a webservice, deserialized, queried and then sent back.
I was wondering if it is possible to convert a hibernate linq query to hql to be sent over the wire.
Is there another route I am missing?
I think I've seen ADO.NET Data Services as advertised to work with NHibernate:
http://wildermuth.com/2008/07/20/Silverlight_2_NHibernate_LINQ_==_Sweet
http://ayende.com/Blog/archive/2008/07/21/ADO.Net-Data-Services-with-NHibernate.aspx
This is an old post, and not sure how maintained this feature is, but its worth a shot.
I have a suggestion to you. Do not try to serialize query. Rather provide your user with an ability to compose arbitrary LINQ expression. Then send the expression over the wire (there is a gotcha here, since expressions are not serializable) to your server.
I have recently submitted to NHibernate.Linq project a change to their NHibernateExtensions class - a new ISession extension method List, which accepts an expression and fills the given list with the respective data, much like ICriteria.List method. The change was accepted (see here) so downloading the recent version of NHibernate.Linq should contain this method.
Anyway, you can find the details of this approach here.