When it comes to multi-tier applications with modern ORMs, I often don’t know how to create specific classes in order to adhere to the so-called “best practices”, and also pay attention to performance requirements.
Please note that an application can have any number of the following types of objects:
Domain objects are rich classes that contain business logic (right?) And, depending on the capabilities of ORM, can be directly associated with a persistence construct.
DTOs are simpler classes that share business logic to pass data to internal and external clients. Sometimes they flatten, but not always.
View models - they are similar to DTO because they are simpler and devoid of business logic, but they are usually quite flat and often contain additional bits related to the user interface that they “serve”.
The problem is that in some cases, matching objects in a domain or any retention-oriented class with a simpler object, such as a DTO or ViewModel, does not allow you to make important performance optimizations.
For example:
Let's say I have some domain objects that look like this:
public class Event
{
public int Id { get; set; }
public string Name { get; set; }
public DateTime EventDate { get; set; }
public Band Headliner { get; set; }
public Band Opener { get; set; }
}
public class Band
{
public int Id { get; set; }
public string Name { get; set; }
public Genre Genre { get; set; }
}
In the real world, this can be much more complicated, with different business logic, possibly with some validation challenges, etc.
If I open an open API, my DTO can be very similar to this example, without any business logic.
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public class EventViewModel
{
public int Id { get; set; }
public string Name { get; set; }
public DateTime EventDate { get; set; }
public int HeadlinerId { get; set; }
public string HeadlinerName { get; set; }
public int OpenerId { get; set; }
public string OpenerName { get; set; }
}
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