We have multiple model projects using codefluent (M1 and M2).
Is it possible to have one model project (say M1) using type reference of another model project (M2) ?
I tried adding project reference or existing item in model but none of them worked.
The import feature doesn't seem to be the way to go either
Shall I consider having only one model project for my solution ?
Thanks for your answer,
I think you want to create a relationship between entities of both models.
If so, it's easier to have only one model. If you create multiple models because of their sizes, you may be interested in parts and surfaces to split it (blog post about surfaces).
If you want to have multiple models, I think it's possible to create relationships between entities (but I didn't test it). You need to create the entity in both model and play with the producer specific attribute enabled (cfps:enabled, cfom:enabled, etc.). Unless you really want to do complex things, I think you may stick to one model.
Related
When working with EF (v4,5,6) I have always used Database-first (I was mistakenly under the impression this was the only way to generate Entities from existing tables, EDMX, etc). But today I tryed Code-first, and it can also generate the POCOs (in a different way, no EDMX, different connection string, less cr8p lying around, etc..!)
So far, the usage of EF for CRUD appears to be exactly the same, can anyone who has used both please confirm there is nothing different (in usage), or gotchas I should be aware of?
And a supplementary question is, can I generate both in the same project ? (Not that i want to, but existing proj has EDMX within a folder, can I create another folder and generate Code-First Entities (different set of tables only), so i end up with DBContext and DBContext2 ?
Yes, the usage is the same. If you check the generated code you'll see they use the same System.Data.Entity.DbSet properties and they both inherit from the same System.Data.Entity.DbContext class.
Yes, you can generate both in the same project, but does not makes much sense, because you have to maintain both of them if the DB changes.
I have three projects (WCF projects, not clients), I have one database for all, now how will I use EF with this? should I make a fourth project which will have the db context and the entities and then add a reference to it in all three projects? or should I just have a separate context for each project and just add the tables i need for each project? some of the table are really used everywhere. so what's the best solution for this?
Another question: should I expose the EF db context in the separate project so other projects can access it? something like:
MySeparateProject myPr = new MySeparateProject();
using (var db = new myPr.DBContext())
{
// do stuff with entities
db.SaveChanges();
}
I think the cleanest thing to do is create a data access project (class library) that contains just your models and db context, and reference that from all of your other projects.
Some people will say that you should make one class library with just the models, and then have yet another that has the DbContext, and the have repository classes, and then.... I feel this is overkill for the majority of projects. Having the models and context in one place just makes it really easy to keep all the dependent projects consistently in sync when it comes to data access.
Here's a typical project structure for me:
Here, Squelch.Data contains all of my models and db contexts, Squelch.Core contains core business logic, and my two "applications" (Squelch.Portal ad CdrImport), and the various test cases, all reference these base class libraries.
I would create a separate data access project. It is good practice to separate your data layer out anyhow. Depending on the nature of the project and how you want to test it, you may want to take a look at something like the repository pattern (though there is debate about its value with EF).
http://msdn.microsoft.com/en-us/library/ff649690.aspx
I've system that has a primary data model to perform most of the work.
The model has quite a few tables and with performance in mind when I came to add an administrative feature to the application I decided to use a second separate data model.
All works well until my second data model needs to access a table that is also in the primary data model. Now, from digging around I can see this can cause problems.
The two possible workaround I've come up with are to either:
Put the data models in separate projects.
Use views / stored procedures for accessing the table in question when required.
Method 1 seems the simpliest but I'm concerned about whether there would be any performance loss. Method 2 seems a bit messy and takes the point out of using EF.
Before I plump for using method 1, is there an easier work around that I could use?
In the end I decided to put the two data models into separate projects and I've there hasn't been any slowdown that I've been able to notice (I've not done any benchmarking but it's passed the perception test).
In one of her online tutorials EF guru Julie Lerman says that you should put your data model in a separate project anyway, so I don't think this has been a bad workaround.
I am working with 2 models in the same project, because I connect to 2 different databases. I have put different namespaces using "Custom Tool Namespace" on *.tt files but it is not necessary. It generally works, but it cannot handle situation when the entity (table) with the same name is in both models. When you save one model the entity with the same name is deleted from the second model.
I'm new to the Entity model thing and i'm looking for an advise how to organize my Entity model.
should i create one entity model file (.edmx) which will contain all the tables in my database or should i break it logical files for user, orders, products, etc.
Please let me know which one is better and what the pros/cons (if any) of each alternative.
Thanks.
I'm going to go against the grain here. I've built 2 large applications with EF now, one with a single edmx and one with several. There are pros and cons but generally I found life to be much easier with one edmx. The reason is that there is almost never a real separation of domains within an app, even if there appears to be from the start. New requirements pop up asking you to relate entities in different edmx's then you have to refactor and continually move things around.
All arguments for dividing will soon be obsolete when EF 5 introduces Multiple Diagrams, which is the only real benefit for dividing edmx files in the first place. You don't want to have to see everything you're not working on and you don't want a performance impact.
In my app with the divided edmx's we now have some duplicate entities to get the benefit of navigation properties. Maybe your app has a true separation of domains, but usually everything connects to the user. I'm considering merging two of the now but it will be a lot of work. So I would say keep them together until it becomes a problem.
Having one big EDM containing all the entities generally is NOT a good practice and is not recommended. You should come up with different sets of domain models each containing related objects while each set is unrelated and disconnected from the other one.
Take a look at this post where I explained this matter in detail:
Does it make sense to create a single diagram for all entities?
i think we should keep multiple edmx files in our project. it's like 1-edmx file -- one aggregate (collection of related objects). as per ddd (domain drive design) we can have more than one aggregates in our model. we can keep one edmx file for each aggregate
I am trying to figure out if it is correct to put in the fields of the particular class a reference to an object/collection that this class is related with.
Let's say I have a class University that aggregates many instances of Student class. When I put on my diagram both classes, I add the relationship of aggregation between them.
And now the question: Can I add in University a field like 'students : Student[]'? Do I have to? Or maybe I must not?
Thanks in advance,
Piotr
Attributes own association properties in UML 2. This is new and it is not always easy to understand the concept. I didn't understand why we need an attribute till I have seen the following demo.
The golden rule is that attributes should be created in order to save association information in the model. I have found an interesting teaching session on association and aggregation in UML 2.
It is a 2m30s flash demo
http://www.download-omondo.com/AggregationAndComposition.swf
The above association creation is for expert level, I mean modeler who wants clean design and clean model as well as perfect metamodel. If you don't care then just create an association at model level and it would do the job but the code generation will not be done. It means that mappings for database will needed to be created at code level later by developers.
To understand the difference between both kinds of associations see this other flash demo at: http://www.download-omondo.com/association.swf
It depends on what you are doing with your model, but generally, you shouldn't have to use an attribute for this, you can use an association instead. Associations are able to contain more information that attributes, such as whether they are composite or shared, which ends are navigable, multiplicity on each end, named endpoints, etc.
One benefit of associations is that one association can actually represent a property on each class it is connected to, while an attribute only represents a property on the class it belongs to.
So, in your case, University has Students, so you'd draw an association from University to Student, naming each endpoint and setting the multiplicity correctly.
Now when you go to generate code from your model, just be sure to take into account associations as well as attributes. This way you won't need to add the properties both as attributes and associations, just as associations. I have a few diagrams I've tested this approach with, generating sql and php code from the xmi via an xsl transform, and it works quite well... if you'd like more details I can dig it up.
There are 3 types of relations : association, aggregation and composition. composition is a specialization of aggregation, aggregation is a specialization of association.
Using one or the other depends on the phase of your analysis. You could just use association in first draft and then refine it later to aggregation or composition, the difference with aggregation is that a student had no meaning out of one University Universe. If there are several universities instances, it would be aggregation rather.
If you use relations, there's no need to and you shouldn't add students[] because it is redundant. And if you do that you lose the semantics of the 3 types of relations.