For many years NHibernate reigned as the premier ORM for the .NET framework and despite the successes of Entity Framework many people still consider it their first choice for new projects. But a lack of developers may severely hamper its future.
Currently there are only two significantly active developers, Alexander Zaytsev of Fourth Media and Oskar Berggren. They are making great strides in preparation for NHibernate 4 on .NET 4.0, but that doesn’t change the fact that .NET 4.0 was released over three years ago. Since then a lot has changed. Most prominently is the introduction of async/await with .NET 4.5, a feature that is rapidly becoming essential for any library that deals with I/O. According to Ricardo Peres, other issues include its lack of support for left joins in LINQ queries, the need for more documentation, and “usage of an obscure collection library called Iesi.Collections”. He continues,
NHibernate’s problem, in my opinion, is lack of leadership. As far as I know, it is not known if the next version of NHibernate will be 3.4 or 4, and what will be there, except, of course, bug fixes, and even less what will NHibernate evolve to, when will it support .NET 4.5 constructs such as async, and so on. The NHibernate Development list is very quiet, and these questions, as well as lots of others, have had no response to this date.
While Entity Framework’s functionality is way behind NHibernate – and believe me, it really is – it is gaining ground. Entity Framework has a leader, a well known team which makes its discussions publicly available and takes suggestions from the community in the form of requests and even code patches, some of which have already been incorporated in the main product. The next major version, 6, was announced some time ago, public betas already exist – and, of course, anyone can get the current version from CodePlex – and it points to a direction. Granted, it is not going to address any of NHibernate’s stronger points, but instead it is moving with what appears to be the current trend, namely, asynchronicity, .NET 4.5 integration and conventions.
Adam Bar echoes these thoughts,
Are there any new features planned for 4.0? Well, there are some, but I can't say the list is impressive. SQL Server 2012 will be supported better (sequences, limit feature), Ingres9 will be also supported out of the box and few other dialects will have some improvements. But, let's admit it, this is not a big deal for existing users. There are of couse several bugfixes and minor improvements done and planned for that version, i.e. in Linq provider (NH-3186, NH-2852, NH-3056, NH-2915, NH-3256), in mapping-by-code (NH-3280, NH-3313). There is also one possibly significant performance improvement with Linq queries done.
This isn’t to say things can’t change. The NHibernate community is still quite large and there are a lot of code bases that cannot be switched from it to another ORM. It is just a matter of mobilizing them.