We have a large array of projects that were built using LinqToSQL and are interested in restandardizing on NHibernate. Most of the ORM we do is pretty straightforward. It occurs to me that there might be a semi-automated way to convert these systems to use NHibernate, perhaps by creating a tool that can point to a DBML and generate corresponding POCO entities and fluent NHibernate mappings.
Has anyone given thought to this or encountered any tools that could speed us along?
Thanks!
You can find a T4 impl at this link, but imho you could try to use the automappings.
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DMS can parse many languages including C# 4.0 and LINQ, producing ASTs. It can carry out source-pattern matches and source-to-source transformations on code, generating revised ASTs, and then can regenerate valid source code. It can likely accomplish your task.
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I'm looking for software that can do the mapping for me in nhibernate.
I looked over for this but the only thing that I found was tools for fluent. I couldn't find anythings for clean nhibernate.
Is their such a tool?
Nhiberante 3.2 has build in mapping by convention ability.
Another way is to use conform library.
You may also want to take a look at the NHibernate Mapping Generator
Just to complement the other answers, there are tools such as Visual Nhibernate that inspect your database and generate your mappings while providing hooks for you to customize the code generation process.
I would basically like to know things such as:
Advantages/disadvantages between the two?
Similarities/differences between the two frameworks?
How are they similar/different architecturally?
How much boilerplate code is needed to use each?
Can the Entity Framework be used efficiently outside of Visual Studio compared to NHibernate? Is the Entity Framework more efficient than NHibernate when used with Visual Studio?
Note: This question refers to the Entity Framework 2 (currently still in development).
Disclaimer: This post is based on my current knowledge of what the next version of Entity Framework will be like. That might be inaccurate or it might change until the next version is actually relased.
General Approach:
The main approach of Entity Framework (EF) is using their graphical designer tool to create an Entity Data Model and to generate domain classes as well as mapping from that model. There is support for other approaches as well, but that way of working will probably always be the main one.
NHibernate (NH) is a text based tool which requires the user to write all the domain classes and mapping manually, if you don't turn to third party software for code generation, such as MyGeneration of CodeSmith, or additional convention over configuration support, such as Fluent NHibernate.
Code Generation:
Code generation is a major part of standard EF usage, either by using their graphical designer tool or by using their command line tools. The availability of both GUI and command line tools is a plus since makes EF easy to get started with as well as allowing for more advanced usage that can be automated, for example in a build process.
Code generation is not supported by NHibernate, except for the schema generation stuff if you want to count that as code gen. You can get code generation if you turn to third party software though.
Database Schema Generation:
EF will add support for model first development, by allowing the user to generate a schema from an Entity Data Model. NHibernate has had schema generation support for a long time. The difference here is how you create your "model", as mentioned earlier.
LINQ:
EF will have improved their whacky LINQ implementation from v1 and NH have now reached version 1.0 of LINQ to NH, so there should not be any major differences between the two in that regard.
POCO:
EF will add better support for the Domain Driven Design approach and the use of domain classes that are separated from the data access layer. However, since POCO is not the main use case of EF I can't really see how their POCO support could ever reach the level of NHibernate. The POCO support in EF is still young, and to me it feels more like that it is a bonus if you are a POCO/DDD supporter and you find yourself working on EF for some reason.
The entire NHibernate framework is build for POCO development, by DDD people, and they have reached version 2.1 as well as taking advantage of all the work put into Hibernate on the Java side. NHibernate will probably remain the no 1 choice for the DDD/POCO/ALT.NET crowd for quite some time.
Lazy Loading:
The next version of EF will include support for automatic lazy loading. Automatic lazy loading has been an important part of NHibernate for a long time.
Learning Curve:
Both frameworks are complex and powerful, and hence take a long time to master. But EF is quite beginner friendly since it is integrated into Visual Studio, with its graphical designer tool, and since it can generate a lot of stuff for you without you having to know just about anything about the framework. However, if you want to dig deeper into EF and really learn the framework, you should be prepared to spend quite a lot of time using it.
NHibernate has a notorious learning curve, but some recent improvements have reduced it a bit. Now that LINQ to NH is at v1.0 the query syntax will be easier to understand for developers new to NH, and the Fluent NHibernate project is improving the mapping experience, and even working on automatic mapping, which is getting better and better all the time.
Can anyone throw some light on tools that can be used with NHibernate and which perform the below mentioned tasks:
Generates the Mapping File
Generates the Entity Class
Generates the Configuration file
And also provide information whether these tools are open source or licensed.
Thanks
One tool I've used that did a decent job was CodeSmith. It looked at the existing database and created the entities, mappings and configuration file. However, this is only to be used as a starting point as there are many tweaks you'll likely want to do to make it more usable and better performing. Things such as when to lazy load vs. eager load, creating subclasses or components. This tool really just mimics the database structure in your entities which is not always the best way to represent in code.
This is a licensed solution but it includes a fully functional demo you can use to gen your files initially. After that, you'll most likely just enhance just as you would your database.
Another is MyGeneration. Same thing, it'll get you 75% of the way there in most cases.
Just be cautious as to which version of NHibernate these tools are producing. They may be using an older version which may have some obsolete code.
I really like Visual NHibernate (http://www.slyce.com/VisualNHibernate/).
Not free, but has a nice set of features, including the definition of templates for the entities, and generating both HBM.XML as well as Fluent NHibernate mappings.
A similar question with some answers you might find useful is already on SO.
NHibernate Generators
As mentioned in that question's answers, fluent NHibernate is a good option. It just went RTM. You can find more info at http://fluentnhibernate.org/
Check out LLBLGen Pro. It's got a competing ORM but can also act as a code generator for nhibernate. Very good for DB first work.
I need to collect some information about existing ORM solutions.
Please feel free to write about any programming language.
Can you tell about the best ORM framework you ever use and why is it better then others?
I used NHibernate and Entity Framework.
Current stable version of entity framework is very immature. It is too difficult, or impossible to perform common tasks. Testing your code is also difficult since you cannot really separate your entities from your data access classes. But it perfectly integrates with visual studio ide. Setting up is easy and updating all the models from database takes just a few seconds. Upcoming version of EF (4.0) will solve some of this problems.
NHibernate is quite powerful. It supports plain old clr objects, so you can work with simple entities. Configurations provide great control in great detail. Framework capabilities are satisfying and it has a large and active community and good documentation. Setting up and updating entities is a little difficult since you must use generators that looks up your database and generates entities and xml files. It may be tricky to find a generator or a template that exactly fits your needs. But once you set all things up, you will love it.
I found LINQ to SQL to be a pretty straight forward solution. The first time I used it, I'd say I had a basic ORM working within a few hours, and was creating LINQ queries with it.
Microsoft has an additional ORM (Entity Framework), which I've heard is more complex but may be useful for highly complex distributed applications with multiple data sources etc.
Overall I found LINQ to be an easy and fast to use ORM.
I have been looking at Telerik Open Access for last few months, in genernal this ORM has been a pain to work with, it was advertised as having extensive linq support but in reality many of the linq features you would normally expect dont work server side and are performed on the client. I also had problems using multiple conditions in a where clause, see my last question. Here are a few things that i found
No support for views
Unable to map more than one entity to the same table
Inheritance and Interface support requires you to make changes to you database schema
No visual designer like LINQ to SQL and Entity Framework
If you want to perform an insert any related entities must be fetched first
Rohan
LINQ2SQL was nice, EF makes sense, but is very complex and SQL Server oriented. NHibernate is special and Telerik OpenAccess (fully .NET / Visual Studio) got a broad set of functionality and professional support.
Since I know the product I can comment on Rohan's concerns:
Existing Views can be used and full Views support is coming up
Mapping more than one entity to the same table "works" for class hierarchies, limitation with reverse mapping exists
Inheritance and Interfacer support "do not require" changes to the the database schema, again limitation with reverse mapping exists though
Visual Designer will come, Forward and Reverse Mapping Wizards allow you already to do anything in an easy way
There is a workaround for the insert issue mentioned and it will be fixed generally
Check out the Telerik site to find happy customers and feel free to use the telerik forums and support resources for any question.
-Peter
Im new to OpenAccess ORM and we are using two products. Reporting and OpenAccess.
I think there are some features that people missed.
OpenAccess uses graphical designers while nHibernate still uses handwritten xml files
OpenAccess is not limited to SQl Server as EF4 and similiar frameworks
using it is easier and the forums are pretty helpful.
With ORM there are multiple possibilities, all depends what you want.
As a real ORM mapper I strongly recomment NHibernate and Fluent NH mappings. You need a lot of research to put together a nice architecture, but then nothing stands in your way. With minimal compromises you get real flexibility.
EF6x (core is not prod.-ready IMHO) is called an ORM, but what it generates is more closer to a DAL. There are some thing's you can't do effectively with EF6. Still, this is my favorite tool for a read-model, while I do combine it with NHibernate (where NH I use for a DDD/write model).
Now to performance - its always pro and cons. If you deep deeper into ORM architecture (see my article: avoid ORM bad habits) then you will find intuitively the ways to make it faster. Here's my another article on how to make EF6x 5x faster (at least for read situations): EF6.x 5x faster
What are the key differences between llblgen and nHibernate?
LLBLGen is an exquisitely case hardened tool that generates ultimately extensible code. Customer service is second to none and bugs are fixed as they are found by one of the finest minds in the business. I have had 5 hour turnarounds on obscure, affecting only me, bugs.
I am currently cutting my teeth on nhibernate and have to say that the apprehension that kept me from it for so long was not misplaced. It is a great tool with a huge user base but inherently, the mapping file / mapping classes / mapping attributes strategy is at the same time soft and brittle.
This is my opinion, no need for punitive downvotes because I am criticizing nhibernate.
LLblgen is a commercial tool, it uses designer based configuration to generate the classes for data access.
Nhibernate is an open source free tool that uses xml based mapping files to map your objects to the tables in the database.
I prefer Nhibernate over LLblgen.
Taken from the overview page of llblgen's homepage:
LLBLGen Pro, the #1 O/R mapper and data-access tier generator for .NET, generates a complete data-access tier and business façade/support tier for you (in C# or VB.NET), using an existing database schema set. In seconds. The generated .NET code is compiler-ready and can, being compiled by the .NET C# or VB.NET compiler, be used immediately by other applications.
So yes, its an ORM mapper as well, plus loads more.