C# – Good Features for an ORM

corm

I'm currently working on putting together a fairly simple ORM tool to serve as a framework for various web projects for a client. Most of the projects are internal and will not require massive amounts of concurrency and all will go against SQL Server. I've suggested that they go with ORM tools like SubSonic, NHibernate, and a number of other open source projects out there, but for maintainability and flexibility reasons they want to create something custom. So my question is this: What are some features that I should make sure to include in this ORM tool? BTW, I'll be using MyGeneration to do the code generation templates.

Best Answer

For the love of all that's holy (and the women and the children), do everything possible to convince them not to go with a custom O/RM solution. Why are people wanting to re-invent the wheel when there are perfectly-good, open-source wheels already in existence?!?!

Related Solutions

The “N+1 selects problem” in ORM (Object-Relational Mapping)

Let's say you have a collection of Car objects (database rows), and each Car has a collection of Wheel objects (also rows). In other words, Car → Wheel is a 1-to-many relationship.

Now, let's say you need to iterate through all the cars, and for each one, print out a list of the wheels. The naive O/R implementation would do the following:

SELECT * FROM Cars;

And then for each Car:

SELECT * FROM Wheel WHERE CarId = ?

In other words, you have one select for the Cars, and then N additional selects, where N is the total number of cars.

Alternatively, one could get all wheels and perform the lookups in memory:

SELECT * FROM Wheel

This reduces the number of round-trips to the database from N+1 to 2. Most ORM tools give you several ways to prevent N+1 selects.

Reference: Java Persistence with Hibernate, chapter 13.

Php – Good PHP ORM Library

Look into Doctrine.

Doctrine 1.2 implements Active Record. Doctrine 2+ is a DataMapper ORM.

Also, check out Xyster. It's based on the Data Mapper pattern.

Also, take a look at DataMapper vs. Active Record.

Best Answer

Related Solutions

The “N+1 selects problem” in ORM (Object-Relational Mapping)

Php – Good PHP ORM Library

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