I am using Entity Framework for my .NET application. I have been able to return objects and their directly-related objects as well (very convenient), but I am having trouble getting the objects of those objects.
IEnumerable<Lot> i = (((ObjectSet<Car>)_carRepository.GetQuery())
.Include(a => a.CarTypes).Take(10).ToList()
This works and I can access carTypes, however I cannot figure out how to access tables associated with CarTypes (e.g. tables which have fields associated with the car types).
I tried to use a Join however I was unable to figure out how to get it to work right.
All help appreciated.
Include can be chained, but you have to keep in mind that it uses strings rather than lambdas. So you do .Include("CarTypes.Company") if you want a two level include. You can also chain Include statements which means including more than one branch from the same top level--eg. .Include("CarTypes").Include("SomeOtherTypeFromTheSameParentAsCar").
You should keep in mind, though, that deep Include statements may not produce the best possible performance because every part of an Include just adds on to the one query that you are building so you will get a larger and more complex query which does a whole bunch of joins under the covers. Sometimes it's more effective to do a few Includes in one query and then issue a second query to get the rest of your data or something like that.
With EF4 you can also setup lazy loading which can sometimes make this kind of thing even easier (but of course it produces multiple roundtrips rather than one or two very large roundtrips).
I believe you can chain Includes... So you could have something like
.Include(a => a.CarTypes.Company)
If you're just using one or two fields from each type, one possibility might be to create a view in the DB. Then you could add this view to your EF model and access those properties directly.
Related
Can anyone actually explain, in layman's terms, what is a real-world use case for the set operation's options?
While I fully understand what set with merge does, as well as merge beeing a boolean and mergeFields being an array of fieldPaths, I cannot think of cases in which mergeFields might be of any use.
I also understand the fact that mergeFields basically acts like a mask for the object passed to the set operation, but I still cannot think of how is it so useful that it actually got implemented within the SDK.
Can someone shed some light?
After looking through the documentation, there seem to be two reasons why you might want to use one vs the other:
mergeFieldPaths/mergeFields trigger an error when passing in field values that don't currently exist on the document while merge will add in those fields if they don't exist. The error is good for safety purposes if you're concerned about typos/writing to incorrect field paths.
This one is just a guess, but the documentation indicates mergeFieldPaths/mergeFields ignores AND leaves fields untouched while merge ONLY leaves other fields untouched. It's possible there's some performance advantage to using mergeFieldPaths/mergeFields esp for documents with a ton of fields. The difference might be direct access vs still needing to look at unspecified fields to identify the matches in some way.
SetOptions Reference
I got a complex data structure like this:
leve1Model->1:level2Model->n:level3Model->1:value1
->1:level4Model->1:value2
What I need is to find all level1Model instances which's level2Model instance contains one level3Model instance which has a certain value1 and which's level4Model instance also has a certain value2.
I am relatively new to Extbase and it's Database abstraction, but I figured I could do something like:
$query->contains('level2Model.level3Model.value1', val1),
but this gives me an error about an unsupported property value1. But even if it worked I don't know how I would make sure that the contained instance also meets the required level4Model->1:value2condition.
So is there a way to properly use the abstraction layer for this kind of query (and how would I go about that?) or do I have to resort to plain sql?
The query builder will not help you much here. If the second level model is stored within an object storage you could query against the uids of these objects. But that's as far as the query builder will take you. Your query is too complex. You would have to split the query into multiple parts and re-filter the results but the performance might be bad. I would suggest using the helper functions for sanitation etc. but passing it the finished sql statement parts (fields, from, where etc. ). Alternatively you could rethink the data structure of this is an essential part of your app to make it more extbase compliant.
This is entity framework:
var department = _context.Departments
.Include(dep => dep.Employees.Select(emp => emp.ContactTypes))
.SingleOrDefault(d => d.Id == departmentId);
Here I expect one department to be returned containing all related employees and all contact types for each employee.
This is ormlite servicestack:
I have no idea. When I look at the docu/samples: https://github.com/ServiceStack/ServiceStack.OrmLite
They write:
Right now the Expression support can satisfy most simple queries with a strong-typed API. For anything more complex (e.g. queries with table joins) you can still easily fall back to raw SQL queries as seen below.
I have seen there is a JoinSqlBuilder class but I do not think it can return nested collections.
Maybe what I want is not possible but maybe I can do a compromise like get all employees for the departmentId. Then I inmemory foreach the employees and fetch all contact types for a certain employeeId. Creating the hierarchy and assigning the lists would still be my job.
But I hope there is a shorter solution.
What would also be fine is when the query however it might look like return an object (Dynamic?) with 3 flat properties: Department, Employees, ContactTypes and assign thoese properties to my DTO.
Ok, please don't take this as a definitive answer, but more just my take on the situation (I don't use service stack very much) however...
When I first started to use EF many years ago, I came across a similar situation, where the references just would not load. Like you I was faced with the likely hood of having to enumerate the individual collections myself and write a lot of extra code for an operation the ORM should be able to handle easily.
What I ended up doing, was to use auto-mapper, which basically reduce all the multiline loops I had everywhere to a single line mapping statement.
Granted, I still had to do one mapping statement for each linked property, but it reduced the code I had to write, and more importantly got me up and running until EF improved, or I found a better way of doing things.
Let me stress, I'm not proposing this as an answer, and it's a bit big for a comment, I'm simply suggesting shifting your thought in a different direction, that may help a better solution come to the surface.
I'd like to learn about using catalogs correctly.
I have about 30 useful content types, about 50 indexes in catalog.xml, and about 45 metadatas. There are just three types which account for most of the site's data - and I may need millions of these. I've been reading, and there's lots to do, but I want to have the basic configuration right before I begin all that.
This page told me that any non-default indexes should not be added to the portal_catalog. I've even read people explaining how removing one, or two of the default indexes makes a performance difference.
My question is: what are the rules for dividing up the indexes into different catalogs, and for selecting which catalog(s) index which type(s)?
So far I have created one additional catalog, used to catalog all indexes for my 'site-setup' objects (which I have caused to no longer be indexed in portal_catalog). The site-setup indexes are very often used, but more rarely modified than others, so I thought it was correct to separate them from objects which are reindexed more often. I'm not sure if that's the main consideration though.
Another similar question (a good example of the kind of thing I want to solve): how would you handle something like secondary workflow review_state variables? I give each workflow's review_state variable an index (and search on them quite often), but some of my workflows are only used on just a few types. (my most prolific objects have secondary workflows...)
I'd be very grateful for advice!
Campbell
This won't cover everything but I'll bring up some points..
Anything not in the portal_catalog won't work with collections, folder_contents view, getFolderContents method, search, portlet collections, related items(I think) and anything else the assumes you're using the portal_catalog.
I like to use an additional catalog when I need to be able to query the data but it only affects a sub-set of the content objects.
Use collective.indexing to speed up indexing operations.
Mount the catalogs on their own mount points so you can cache them differently from the rest of the site(so you can cache the whole catalog). Then, you can even serve the the catalogs from dedicated zeoserver.
Also, if your content doesn't have to be cataloged by the portal_catalog(with all the constraints listed), you may even want to think about if you need it as a full-fledged (archetype|dexterity) type in the first place. You can use a more slim repoze.catalog to catalog arbitrary objects(which could be very simple data) for whatever your purpose is and get even more performance. Or better yet, look into Solr for indexing it for VERY good performance.
On more thing, depending on the type of data you're storing, you could even look into using a relational database for a data store. But I don't know what kind of queries, indexes, data, etc you have...
30 different types seems like a lot but I don't know what your use case is. Care to share? Perhaps there is a better way to do it.
I have a database I'd like to create an entity from, and then generate RESTful output.
My objective is to add a property to one of the tables once it becomes an entity. The data for that property would be one I'd come up with through calculations done on a few different fields in the table. From there, the code generator would create RESTful output like it normally does.
I have managed to be able to update the SSDL, CSDL, and the mapping sections of the edmx file along with using the SampleEdmxCodeGenerator as a custom tool. When I have all the sections in the edmx file filled out with my custom property, the svc fails because (I'm assuming) the property doesn't exist in the database. If I leave the property out of the SSDL, but put it in the client schema (CSDL) and the mapping section, I can't build my project.
I've modified the partial class and added to it, but the problem there is that I need to populate the methods on the creation time of the class, and I haven't been able to do that yet.
Am I headed in the right direction, or is this not possible? It seems like I should be able to do this with minimal effort, but I keep hitting walls.
I think you're taking detours to get where you want. I haven't used either of these approaches (recently), so they might not do exactly what you're after, but you could try this:
Create a partial class file right next to the .edmx model, which has the same name as your entity.
In it, specify the property you want as a read-only property, that does the calculations on each get.
Partial Classes and Partial methods were the first part of my answer. What I'm essentially trying to do I can't do. I can manipulate data that is returned by using partial methods and partial classes. I can plug the OnmethodnameChanged() method to format the data how I'd like it to be shown, but that only gets me part way to my desired result.
What I would also like to do, is create a property c, which doesn't exist as a column in the database (and therefore does not exist in my entity), calculated from a couple different properties in the database (say a and b), and then add property c to the entity framework class. In doing this, I figured it would then get generated into the RESTful webservice output.
A problem that occurs comes from the need for the class to update any changes you make, and have it propagate back to the data source. I didn't care about that, because I want my property to be read only. From what I've gathered this isn't possible.
For reference, these two posts really helped:
Adding custom property to Entity Framework class
(I can only post one url currently, so here is the address to the other article)
social.msdn.microsoft.com/Forums/en-US/adodotnetdataservices/thread/b7a9e01d-c5c2-4478-8f01-00f7f6e0f75f
What I've decided to do, is to expose my entity as I've done so far, then consume the RESTful service that manipulates data and reformats it, and introduces needed properties. I'll turn the results into my own data object, and use that as a datasource to be exposed by yet another RESTful web service. I think this website gives a good example on how to expose a custom datasource.
mstecharchitect.blogspot.com/2008/12/surfacing-custom-data-source-in-adonet.html
If for some reason that is too slow, I suppose I could just make another table in my database that has a reworking of the data, and the calculated output in a format I'm looking for. The thing I want to avoid is having my resulting client having to do any of the data manipulation since it will be on some micro devices like palms, iphones, and blackberries.
Hope that helps anyone else with the same problem. It seems that is a shortfall in the current version of Data Services, but to some extent, I'm sure they'll be addressing it in later versions. Maybe T4 and .net 4.0 will be addressing it. I'm not sure.