To be able to represent external data, it must implement IEnumerable

It must implement IDisposable.

It must implement IQueryable

It must implement IEnumerable.

To be able to represent external data, it must implement IQueryable or IEnumerable.

It must implement IQueryable or IEnumerable.

To be able to represent external data, I must implement IQueryable

LINQ (Language Integrated Query) technology that allows you to standardize access to data from the layer.

Separate compilation units that allow you to create independently developed and tested components.

The abstraction allows the user layer to implement the selected functionality in several different ways.

Abstraction (Interface, abstract class) allows you to hide irrelevant implementation details in front of users and allows you to work simultaneously on a foundation of a common contract.

The reflection that allows access to the program's metadata (layer) and the use of a layer without direct access to the definition of functionality offered by its API (application program interface).

No specialized concepts, constructions, and technologies are necessary to apply the selected layered architecture in practice.

If one object wraps (creates) another object inheriting from the IDisposable interface, it must implement the IDisposable interface, as in the example below:

class UsingIDisposable: IDisposable
{
   private Stream m_Stream;
   //
   // ...
   //
}

The object's end of life is immediately handled by calling the Dispose method if it:

• implements the IDisposable interface, and
• is created by the using statement, and
• the block of the instruction has ended.

The object end of life is immediately handled and the resources released if it:

• implements the interface IDisposable
• and the method Dispose is called in the program

If no program variable has references to it the object is immediately deleted and resources associated with it are released.

The object does not have to be manually deleted using the IDisposable.Dispose method or by using the using statement if we release external resources via other methods of this object, eg Stream.Close.