Trying to wrap my head around the best approach in modelling a database when we are using Entity Framework 4 as the ORM layer. We are going to use asp.net mvc 2 for the application.
Is it worth trying to model using the class diagram modeller that comes with Visual Studio 2010 where you graphically configure your models into the EDMX file and then generate out the database structure?
I have run into a bunch of non trivial issues and for complex many to many mappings or multi primary key entities the answer is not that obvious even after poking around a while with the tools.
I figure its easy at this point to give up and start modelling the DB using real, working DB modelling tools and then try to generate out the EDMX from the database, rather than trying to do the model first approach.
It's really a matter of preference. If you are comfortable in SQL server that's probably the best place to start. But if you are more of a C# programmer, it's sometimes easier to start in the EDMX designer, make the model and then ask it to figure out what the database should look like.
Of course if you do go model first you'll still need to go in to SSMS and add indexes and maybe rename some FKs and tables more to your liking. Then you can bring the model back up to date with an Update from Model.
Modelling inheritance is also something you'll need to do in the designer, but again you can either do it in SSMS or in the EDMX designer. For inheritance I mostly prefer SQL first because there is the explicit decision as to what form of inheritance you want - per hierarchy, per class, or per concrete type.
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I'm just starting to learn EF and now readind about Code First workflow. From what I gather, you would design your objects first and then the database would be created based on those objects. I can't seem to see the good in this. Why would you let your database schema be dictated by the hierarchy of your objects? Would you be able to optimize your database using Code First?
Also, as I have not read far enough yet, does Code First fully support DBMS features (indexes, triggers, sp, etc)? I ask as I've read in some articles that this is what most preferred (Code First). I have seen something about Code Second which is from what little I've read, I think is much better (existing database, but code centric development?), but maybe I'm missing something or haven't yet read enough and you guys can clear those things up. Thanks.
The capabilities of code first are the same since you have the same ability to express all the features of EF manually in your code. The main difference is that you don't use a designer to generate your EF code. This offers some benefits since you can decouple your entity classes from the EF context. The main benefit of this is that you can use plain old c# classes that aren't necessarily tied to EF if you decide to switch to another orm down the line.
The downside of course is that you have to hand code the entire model.
Keep in mind that you don't have to generate the database from your code. You can code against an existing database.
I'm working on an application that interfaces with a slightly odd database. The design of this database is pretty bad; there are basically no foreign keys (although there are columns that reference other tables, they're not set as keys), columns are named very ambiguously, and the structure does not lend itself to the kind of logic I'm aiming to do (mostly, it forces joins for operations that should be simple, and leaves you trawling through needlessly massive tables for things that could have been split).
Unfortunately, I'm stuck with this database. It's being replicated off a third-party system, so I can't change the table structure or anything. I can add stored procedures and views, though.
In the application, I've come up with a set of classes that I can work with much more easily. I've got quite a bit of experience with Entity Framework, so I'm planning to use that. My initial hunch is that I can add views to the database that return things in the format of my classes, and then from there on out just pretend that they're tables. I've never tried anything like this before, though, and I'm not entirely sure how to proceed.
How can I use Entity Framework to map my classes to these views? Note that it kinda needs to be my POCO classes, rather than anything EF auto-generates - is there a way to tell EF to map existing classes?
If you use code first then Entity Framework will generate CreateTable instructions in the migrations. To use a view instead, replace this code with your own Sql to generate the View. See the answer to this question: Mapping Database Views to EF 5.0 Code First w/Migrations
I would also configure Entity Framework to use stored procedures. Then you can tailor the insert/update/delete sql to match the underlying tables. Again, you can do this by altering the sql that is generated for you in the migrations.
Our database has about 500 tables we'd like to use in our EF model. Of those I'd be happy to start with 50 or fewer just to get our feet wet after working in plain ADO.net for years.
The problem is, our SQL server contains many thousands of other tables that exist in our database that have been created through the years and many that are dynamically generated. Believe it or not:
select count(*) from INFORMATION_SCHEMA.TABLES
73261
So that's a lot of tables. I have found that pretty much every tool I've tried to design, build or template EF models or entities either hangs or does not return a list of tables. Even SQL Server Object Explorer in VS2012 won't list the tables and instead shows the Tables folder with a little "x" over the icon. So I can't even select a subset of tables.
What options do I have for using EF? Is there a template where I can explicitly define the tables that I want to use entities for? Even with 50 tables, I don't want to hand code each one in an empty EDMX.
Using a Database / Code First approach and avoiding connecting Visual Studio to the database at all (i.e. don't create an edmx, or connect with server explorer) would allow you to do this easily. It does not give you any of the Model First advantages, but I think it sounds like your project would be better served with a Database / Code First approach anyway as:
You have an existing Model, and are not looking to push changes from your EDMX to the DB
You are looking to implement this on a subset of your database
This link has a good summation ( Code-first vs Model/Database-first ) with the caveat that in you case a Database/Code First approach does not have you pushing changes from code to the Database, so the last two bullets under code first apply less, and yours is a Database/Code First hybrid.
With 70k tables I think that any GUI is going to be tricky. When I am saying Database / Code First, I am trying to convey that you are not using the code to create / define and update your Database. Someone may be able to answer this more succinctly / accurately?
I now this is an old question. But for those who land here on a google search. The only tool I have found that actually works with thousands of tables is The Sharp Factory.
It is an ORM. Pretty simple to use. So if you are looking for an ORM that can work with a large number of tables and does not require you to write "POCOS" or "Mappings" or SQL then this is the tool.
You can find it here: The Sharp Factory
I'm bit confused: with all the evolutions of EF i'm not sure where i'm now.
*Is EDMX a choice of the past and should be used any more ?
*If so what is the best choice ?
*I hate edmx, can i upgrade to code first ?
It is not clear what all this EF versions are to me
Thanks
Jonathan
For a lot of apps you can start using Code First if you want to. The one big thing Code First doesn't support yet is mapping to stored procedures. (You can still call stored procedures, but you can't map entity CRUD operations to them.)
That being said, doing Database First with an EDMX is still absolutely supported and a fine choice, especially you like using the EF designer.
EF 4.1 and above fully support both Code First and Database First.
Personally, I would almost always choose Code First, even with an existing database, because I'm a code-centric person and would rather keep all my mappings in code where I can easily refactor, manage in source control, split into multiple files, etc. For me, it's much easier and nicer to deal with code artifacts than monolithic XML documents.
This is how you should evaluate your Entity Framework usage:
1) EDMX is a totally valid option specifically if you have an existing Database and want to generate your entities based on your database schema. One of my favorite benefits to this can be rapid data layer development with low risk. Also mapping stored procedure results to classes is always nice when you have complex existing stored procedures to work with.
OR
2) Code First is a totally valid option specifically if you want to create you database based an object oriented data model. With code first its easy to make big refactors that you don't always think of till implementation time. Source control is more common with code and shelving/rolling back are beautiful features.
TL;DR version :
They are both totally viable options. Neither are outdated ;nor shall they be any time soon.
We had performance consideration in warm up EF Code First. EF Code First take some minutes to start, because we have thousand Entity. so this bottleneck enforced us to Use EDMX, and used Interactive Pregenerated to Create EDMX from Code First in First Run after entity Model changed, and at Other First Run warm up time considerably lowered.
but story not end at that. after doing that we saw in Development area we have many change in Entity Model, so after each change EDMX File should be recreated(update) very often. so we decide to Create EDMX Programatically and Optimize that creation for our Entity Models.
We're currently a Linq to SQL shop but evaluating Entity Framework. One thing that always frustrated me with L2S is how messy the DBML canvas became after putting more than say a couple dozen tables on it. It just became one large mess.
I'm wondering if EF handles this any better? What would be ideal (for us) is the ability to have a separate EDM for each of our schema's. That would keep things very neat and tidy. However, I don't know then how we would establish relationships across EDM's.
Can anyone tell me how (or if) EF handles this sort of thing?
Just my 2 cents.
I deeply recommend you to throw away dbml and edmx as well, and move to EF 4.1 code first. It will give you all the power and flexybility you need.
For me it was a no turning back ever. You can find excellent posts of Scott Guthrie about it if you google a little.
Handling this in EDMX is possible but still it is far away from nice or ideal solution especially because it is not supported by designer - you will work with EDMX as XML. Also relations can be only one way, bidirectional relations between EDMX are not supported. ADO.NET team described the whole process on their blog.
If you have separate schema for some set of tables then tables probably represent some separate business domain where the connection to other schemas are not so common. Perhaps isolating the schema in completely separate model (EDMX) can be way to go.