What is poco

Given this class definition, imagine you'd like to unit test some method on Product. You write the test and the first thing you do is instantiate a new instance of Product so you can call its method. And your test immediately fails because you haven't configured a connection string for the DataHelpers. LoadFromDatabase method to use. This is an example of the Active Record pattern , and it can make unit testing much more difficult.

This class is not Persistence Ignorant PI because its persistence is baked right into the class itself, and the class needs to inherit from a persistence-related base class. One feature of POCOs is that they tend to be persistence ignorant, or at least more so than alternative approaches like Active Record. This Product class is a POCO because it has no dependencies on third-party frameworks for behavior, especially persistence behavior. It doesn't require a base class, especially a base class in another library.

It doesn't have any tight coupling to static helpers. It can be instantiated anywhere without difficulty. It is much more persistence ignorant than the previous example, but it's not entirely ignorant of persistence, since it has an otherwise useless private constructor declaration.

As you can see from the comment, that private parameterless constructor is only there because Entity Framework needs it to instantiate the class when it is reading it from persistence. Assume, for the sake of argument, that both of these Product classes include methods with behavior in addition to the constructors and properties shown.

These could be used a DDD Entities in an application, modeling the state and behavior of products within the system. But what is their relationship to one another, and why do developers so often confuse the two terms? Remember, a DTO's only purpose is to transfer data as simply as possible. They should be easy to create, read, and write.

Any dependency they might have on special base classes defined in third party frameworks or static calls that would tightly couple them to some behavior would break the rules that make the class a DTO.

If the reverse were also true, then we could say that the two terms are equivalent. But we know this isn't the case. In the previous code example, the Product entity that works with Entity Framework has private setters and behavior, disqualifying it from being a DTO.

But as we saw, it is a good example of a POCO. Steve is an experienced software architect and trainer, focusing on code quality and Domain-Driven Design with. What about attributes and data annotations? Category - Browse all categories Software Development. About Ardalis Software Architect Steve is an experienced software architect and trainer, focusing on code quality and Domain-Driven Design with. Style: MLA. More from Merriam-Webster on poco Britannica.

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