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The Estrangement of LINQ to SQL

Tuesday, November 11, 2008

Tim Mallalieu, PM of LINQ to SQL and LINQ to Entities, recently announced:

“…as of .NET 4.0 the Entity Framework will be our recommended data access solution for LINQ to relational scenarios.”

Tim later tried to clarify the announcement in a carefully worded post:

“We will continue make some investments in LINQ to SQL based on customer feedback.”

Although Microsoft may not remove LINQ to SQL from the framework class library just yet, they do appear to be treating LINQ to SQL as an experiment that escaped from the lab – something to minimize until it’s erased from our memories. Many consider the decision inevitable, as the ADO.NET Entity Framework is considered the crowning achievement in Microsoft’s long quest to build a deep abstraction over relational databases.


On the surface the reasoning is sound. The technologies are both solutions in the same problem space, and have overlapping features. Both frameworks use metadata to map relational data to objects, and both implement change tracking, identity maps, and a unit of work class. Each framework also has distinguishing features, however. For instance, LINQ to SQL supports POCOs and implicit lazy loading, while the Entity Framework delivers support for multiple database providers and sophisticated mapping strategies.

The belief is that merging the distinguishing features of LINQ to SQL into the Entity Framework will produce a piece of software that makes everyone happy – but I’m not so sure.

On the surface, conservative governments and liberal governments are both solutions in the same problem space - governance. Both will implement a chief of staff and a head of state, but the implementation details don’t matter. It’s the philosophical differences between conservatives and liberals that determines the quality of life for the individual citizens of the government … and that’s as far as this analogy will go.

Irreconcilable Differences

LINQ to SQL and the Entity Framework promote fundamentally different philosophies.

LINQ to SQL is geared for thinking about objects. There is an “I’ll make this easy for you” feeling you get from the technology with its flexibility (such as mapping with XML or attributes) , and escape hatches (such as ExecuteQuery<T>). The simplicity surrounding LINQ to SQL makes many people think of the technology as a toy, or only suitable for RAD prototyping. The truth is that LINQ to SQL just wants to give you objects and let you go about your business.

The Entity Framework is geared for thinking about data.The crown jewel of the framework is the theoretically grounded Entity Data Model. The Entity Framework’s intent is to promote the EDM as the canonical, consumable data model both inside an application (via technologies like LINQ to Entities, Entity SQL, and ASP.NET Dynamic Data) and outside an application (via technologies like ADO.NET Data Services). The Entity Framework wants the data model to be pervasive.

Some developers like objects, and some developers like data. I think it’s impossible for the Entity Framework to make both types of developers happy 100% of the time. Personally, I prefer the design of LINQ to SQL despite some obvious deficiencies. The Entity Framework wanted to distinguish itself from similar frameworks produced by OSS projects and third party companies, but in doing so I think they missed the key reasons that developers turn to these technologies in the first place. Version 2.0 promises to deliver some of these features, including the ability to do model first development instead of schema first development, but I’m still not convinced that the Entity Framework can ever refactor itself to deliver the simplicity, usability, and philosophy of LINQ to SQL.

What To Do?

There are many suggestions floating around on what to do with LINQ to SQL. David Hayden and Steve Streeting both suggest an open source approach, while Ian Cooper suggests a successor to both EF and L2S.

Here is another idea…

It occurred to me recently that I’ve spent an inordinate amount of time over the last 10 years mapping data. Perhaps this is why I am so suspicious of anyone promoting a canonical data model. Between 1998 and 2001 I was writing commercial software for the mortgage banking industry, and our biggest source of pain was getting mortgage information into our software. We were always on the lookout for a way to map data from spreadsheets, CSV files, XML files, and all the other quirky formats banks had to offer. From 2001 to present I’ve been writing commercial software for the healthcare industry. Again, there is mapping required to process data in the hospital’s format, the government’s format, the insurance company’s format, the third party vendor’s format, and 100 permutations of the canonical (there is that word again) “industry standard” formats.

The mapping never stops at the system boundaries, either. In the last week I’ve mapped domain objects to DTOs, DTOs to UI controls, and UI control status to the UI control status status display. Sprinkle in a little OLAP, a little XML, and some JSON web services with their own custom mappings and I’ve started to think that all software is controlled by a series of carefully constructed hash tables.

The internals of LINQ to SQL could, I think, form the nice foundation for a generic data mapping framework that would be complementary to ORM type frameworks like the Entity Framework. The framework could take out some of the grunt work of object to object mapping, and perhaps through a provider type architecture offer additional mapping capabilities to and from various formats, like XHTML, JSON, CSV. Transforming, massaging, and pushing around data is a fact of life in most large applications and a framework that makes this job easier to implement and test in a uniform manner would be a boon for productivity.

In the end, I hope LINQ to SQL garners enough support to remain viable and evolve, but at this time it looks as if LINQ to SQL is facing an Order 66.