I heard that companies that use Java technologies, they used to build their own custom Framework that wraps Hibernate. However, is it really feasible for their .Net peers to do the same thing with NHibernate or Entity Framework?
This is almost always a horrible idea - I think Ayende sums it up best in this article. In general, you should consider NHibernate itself to be the "wrapper" around your data access - attempting to build an abstraction layer on top of it is probably going to be a losing proposition.
Actually, you should check out some of the articles on .NET Junkie's weblog. He wrote several great posts on how to deal with repositories, queries, commands and so on. We've been using these in a very large enterprise system where we switch between an in-memory dictionary, an in-memory SQLite database and a production environment using SQL Server or Oracle. Obviously, we use NHibernate for this.
I use the repository pattern and a separate project/dll to abstract away the data framework nhibernate / entity framework. this is a good starting point http://codebetter.com/petervanooijen/2008/04/04/wrapping-up-nhibernate-in-repositories/
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I couldn't found a clear answer on that:
Is the ADO.NET Entity Framework a full featured persistence framework like Hibernate for Java?
Is there a any (other) persistence framework in .net? I only found open source frameworks like nHibernate but no clear answer if there is something build-in in .net. What's the best practice to get persistence in .net?
when you talk about persistence layer, usually that is databases or file systems, when you talk about Entity Framework it is called ORMs, and yes, I think in the .Net environment NHibernate and Entity Framework should be two of the most popular ORMs.
ORMs help you to think about your data as objects in your domain, instead of thinking about tables and fields and rows, so it abstracts the technical aspect of persistence and gives you a more model-driven approach while you are writting software.
I use to read a lot about domain-driven design as an architectural guide, but now here in stack overflow I've received many suggestions on using hexagonal architecture, all these patterns and practices help you to buidl better software, and I guess we will never stop learning. So yep, think about ORMs like artifacts to help you focus on more important aspects of your code rather than just making tables and querys. Hope it helps,
I'm interested in using an object relational mapper for an existing system which is a ASP.NET client, ASP.NET Web Services middle layer, and with an Oracle back-end. All database access is done using stored procedures and no SQL is allowed in the web services. I've been investigating NHibernate, Telerik's OpenAccess ORM, and the Entity Framework. I titled this "segregated" because the database is pretty tightly controlled by the DBA's. They also control the database design and reworking the database for adequate normalization (for the object model) is pretty much out of the question. Also, allowing the tool to create any of the SQL is also out the question.
My question is: Given these constraints, which of these tools would allow the best integration for this sort of environment?
None at all.
You're not going to be using 99% of the functionality of an ORM by having everythign done in Stored Procedures.
Probably better to use a Micro ORM like ServiceStack.OrmLite, or Massive, etc...
But looking at any full fledge ORM like NH, LightSpeed, EF, is complete over-kill and will just create more complexity for 0 gain.
Implementing your data access with stored procedures entirely does not mean that you won't gain any value by using an ORM. It just means that you will probably not use some of its benefits.
As for the ORMs you have evaluated, you have probably noticed already that:
All of them support Database First approach, where you can just create your model after the database is already defined, so you won't have to interfere with the DBAs work in any way but to ask for credentials
Entity Framework and OpenAccess provide visual representation of your model out of the box, while NHibernate doesn't
OpenAccess and NHibernate support Oracle, while with Entity Framework using Oracle is not so straight forward
The stored procedures support in Entity Framework and OpenAccess is much more sophisticated than in NHibernate. In OpenAccess you can even map a stored procedure to more than one results set.
I hope that helps.
Let me get this right. Your constraints are:
You have to use an ORM
You cannot modify the database in any way.
You can only use stored procedures.
I think I agree with #Phill. A full blown ORM is overkill when you cannot use it's functionality.
BTW, I once worked on a system like this where the DBA's ruled the roost and mandated only procedures to access the data. Nightmare.
I used Entity framework with a database having around 50 tables and it worked just fine.
But just to see what happens with a larger database in terms of number of tables/entities i tried to implement the Entity Framework to a database that had around 100+ tables.
Once i selected all the tables and clicked on the Finish Button on the Entity Framework Wizard its just hanged my VS 2010 so i could not get any results.
My Questions are as below;
1.If I have larger Database in terms of Table/Entites as described above, Is it a good idea to use Entity Framework?
2.What will be the better approch using Entity Framework to work with database?
3.Should i create multiple DataContext or EDMX files with lesser entites in it?
4.How will these different DataContext interact with each other?
5.Is there any recommended no of tables that should be used while working with Entity Framework?
#Will is correct that the limitation you're seeing is in the designer, but it's not the only one, so Code-First doesn't necessarily fix the problem.
If the designer seems slow, it's inconvenient, but not the end of the world. Runtime performance considerations are another thing altogether. For performance-critical tasks and tuning, you'll want to understand the whole pipeline.
View generation, e.g., takes time. You can move this to compile time with manual work.
1.If I have larger Database in terms of Table/Entites as described above, Is it a good idea to use Entity Framework?
I certainly wouldn't let it stop you.
2.What will be the better approch using Entity Framework to work with database?
3.Should i create multiple DataContext or EDMX files with lesser entites in it?
That's certainly a good approach for many applications.
4.How will these different DataContext interact with each other?
Mostly not. A single, giant data model is often a bad idea due to service coupling. However, you can selectively couple them by sharing portions of the models with includes in EDMX or classes in code-first.
5.Is there any recommended no of tables that should be used while working with Entity Framework?
One way is to use smaller models, as you've suggested. Another way is to work around the runtime performance issues which sometimes come with larger models (see the links I give above). Like any potential performance "problem", write correct code first, then profile and fix the slow parts. Usually, query tuning is more important than model size anyway.
EF, probably yes. The toolset in Visual Studio? Not so much, apparently. For a database this big, you might want to do Code First.
I think EF itself have't performance limitations for count of tables, but have for count of records in particular table. You have to do manual object-db relation (i.e. manual write classes for tables and corresponding attributes) for go away from design problems in VS10.
It's clear approach in Hibernate, but in EF probably not.
Entity Framework is the best way to develop database applications.
I used to develop my applications using LINQ to SQL but since Microsoft is not going to support it in future, it recommends to use Entity Framework.
By the way, Entity Framework 4 in .NET 4 has much better performance than previous versions.
I'm currently developing an enterprise application using Entity Framework and it supports all my needs.
I suggest to use Entity Framework.
I have been using ADO.net since 2002/2003 and most of the application I have developed so far use ADO.net (I do use business objects in my application but underlying data access is through ADO.net)
Question: What is/will be next paradigm of data access technology assuming you are using .net framework and SQL Server?
I am hearing LINQ and Entity Framework but not sure about LINQ or at least its future?
Any advice along with a recommended book will be greatly appreciated.
Object relational mapping is perhaps the next paradigm for data access technology after ADO.NET, although you could say that its already pretty well established. Although Entity Framework is still fairly new NHibernate has been around for several years, and its Java predecessor since 2001.
If you are looking for a good book about NHibernate and object relational mapping in general then NHibernate in Action is good. Its very readable and the first chapter, which is available as a free sample, covers the rationale behind ORM as well as comparisons between NHibernate and other technologies like LINQ.
LINQ is here to stay, what I think you are referring to is LINQ to SQL which while not being very actively developed by Microsoft, is still alive however Microsoft are making it fairly clear that EF is the future.
We have a complex architecture with much logic in unmanaged code that needs database access.
Currently this is via ODBC drivers and MFC classes and we're considering the issues of migrating our abstraction layer to use ADO or ADO.Net. In the latter case we'd have to be pushing database logic back up into the .Net layer. I'm trying to decide if the pain of invoking the database via .Net callbacks is offset by the improvements in ADO.Net.
The Wikipedia comparison was interesting although I'm not sure I believe all the points in the comparison table (eg: does ADO.Net always use XML to pass data?).
A 2005 comparison shows ADO.Net performing dramatically faster.
Microsoft's guide to ADO.Net for ADO programmers suggests we will gain much from going to ADO.Net especially the way that data is available in native (.Net) types rather than solely through OLEAutomation's Variant.
eg: does ADO.Net always use XML to pass data?
No. Sounds like idiot information in wikipedia then.
2 choices. First, I would REALLY get rid of ODBC - and move at least to OleDb driver wise. If possible (tell me - I have a .NET app using an ODBC driver to call a JDBC ddriver to call a third party application server).
Now, you can go both ways - ADO on both sides, managed ADO.NET and expose from the NET layer - but this is really not a programmer decision, it is an architectural thing that should be seen in the major context.
I would possibly go for a .NET layer, possibly with at the same time an OData exposure layer, and try to consume that from the unmanaged layer.