I’d like the community’s take on some thoughts I’ve had about Linq to Sql and other ORM mappers.
I like Linq to Sql and the idea of expressing data access logic (or CRUD operations in general) in your native development tongue rather than having to deal with the ‘impedance mismatch’ between C# and SQL. For example, to return an ObjectDataSource-compatible list of Event instances for a business layer, we use:
return db.Events.Select(c => new EventData() { EventID = c.EventID, Title = c.Title }) If I were to implement this using old SQL-to-C# constructs, I’d have to create a Command class, add the EventID parameter (using a string to describe the ‘@EventID’ argument), add the SQL query string to the Command class, execute the command, and then use (cast-type)nwReader[‘FieldName’] to pull each returned field value and assign it to a member of a newly created instance of my EventData class (yuck).
So, that is why people like Linq/SubSonic/etc. and I agree.
However, in the bigger picture I see a number of things that are wrong. My sense is that Microsoft also sees something wrong and that is why they are killing Linq to SQL and trying to move people to Linq to Entities. Only, I think that Microsoft is doubling-down on a bad bet.
So, what is wrong?
The problem is that there are architecture astronauts, especially at Microsoft, who look at Linq to Sql and realize that it is not a true data management tool: there are still many things you cannot do easily of comfortably in C# and they aim to fix it. You see this manifested in the ambitions behind Linq to Entities, blog posts about the revolutionary nature of Linq and even the LinqPad challenge.
And the problem with that is that it assumes that SQL is the problem. That is, in order to reduce a mild discomfort (impedance mismatch between SQL and C#), Microsoft has proposed the equivalent of a space suit (full isolation) when a band-aid (Linq to SQL or something similar) would do just fine.
As far as I can see, developers are quite smart enough to master the relational model and then apply it intelligently in their development efforts. In fact, I would go one further and say that Linq to SQL, SubSonic, etc. are already too complex: the learning curve isn’t that much different from mastering SQL itself. Since, for the foreseeable future, developers must master SQL and the relational model, we’re now faced with learning two query / CRUD languages. Worse yet, Linq is often difficult to test (you don’t have a query window), removes us one layer from the real work we are doing (it generates SQL), and has very clumsy support (at best) for SQL constructs like Date handling (e.g. DateDiff), ‘Having’ and even ‘Group By’.
What is the alternative? Personally, I don’t need a different model for data access like Linq to Entities. I’d prefer to simply pop up a window in Visual Studio, enter and validate my SQL, and then press a button to generate or supplement a C# class to encapsulate the call. Since you already know SQL, wouldn’t you prefer to just enter something like this:
Select EventID, Title From Events Where Location=@Location and end up with an EventData class that A) contains the EventID and Title fields as properties and B) has a factory method that takes a ‘Location’ string as an argument and that generates a List<EventData>? You’d have to think carefully about the object model (the above example obviously doesn’t deal with that) but the fundamental approach of still using SQL while eliminating the impedance mismatch appeals to me a great deal.
The question is: am I wrong? Should Microsoft rewrite the SQL infrastructure so that you don’t have to learn SQL / relational data management any more? Can they rewrite the SQL infrastructure in this way? Or do you think that a very thin layer on top of SQL to eliminate the pain of setting up parameters and accessing data fields is quite sufficient?
Update I wanted to promote two links to the top because I think that they capture important aspects of what I am after. First, CodeMonkey points out an article entitled ‘The Vietnam of Computer Science.’ It takes a while to get started but is a very interesting read. Second, AnSGri points to one of Joel Spolsky’s more prominent pieces: The Law of Leaky Abstractions. It isn’t exactly on topic but it is close and is a great read.
Update 2: I’ve given the ‘answer’ to ocdecio although there are many great answers here and the choice of the ‘right’ answer is purely subjective. In this case, his answer squared with what I think is truly the best practice given the current state of technology. This is an area that I fully expect to evolve, however, so things may well change. I’d like to thank everyone who contributed, I’ve upvoted everyone who I think gave a thoughtful answer.
For at least 6 years I have been using my own ORM that is based on a very simple concept: projection. Each table is projected into a class, and SQL is generated on the fly based on the class definition. It still requires me to know SQL but it takes care of the 90% simple CRUD, and I never had to manage connections, etc – and it works for the major DB vendors.
I’m happy with what I have and didn’t find anything worth dropping it for.