The repository where the entities ultimately reside generally is not the application's memory itself, but an external storage like a DBMS. This implies that there is a boundary to cross in order to access data. Since this boundary crossing has a cost, EldorADO.NET provides mechanisms to help developers optimize boundary traversals:
- A remote (out of process) source (ObjectContext.RemoteSources) represents a connection to a database.
- A remote source can be queried directly (methods RemoteSource.Fill and RemoteSource.GetDataReader) which provides best performances in one-shot, read-only scenarios.
- A local (in-process) storage (ObjectContext.LocalStorage) is used as a cache to store new and modified data.
- A local storage can be queried as well (methods ObjectContext.LocalStorage.Fill and ObjectContext.LocalStorage.Collect). In this case, no interaction with the remote sources is attempted: only those entities present in the local storage will be returned.
- An objet context (ObjectContext) provides the glue between a local storage and one or several remote sources.
- The object context can be queried as well (methods ObjectContext.Fill and ObjectContext.Collect)
In this case, a preloading stage is inserted before querying the local storage: the entities are first fetched from the remote sources, and fed to the local storage. The query is then performed on the local storage.
The figure below shows the typical architecture of an application using EldorADO.NET:
In addition to the automatic preloading facility provided by ObjectContext's methods, manual preloading is also possible (method ObjectContext.Preload).
These different facilities offer a wide range of possibilities between full control and maximum comfort: you will trade one method for the other depending on performance considerations (data volumes and network latency), on when it is more appropriate to query the database, on what is known to be already present in the local storage, on what it is preferrable to keep in the local storage, or conversely, to query every time and again, etc.
Classes
| Class | Description |
|---|---|
| ObjectContext | An object serving as a bridge between a LocalStorage and one or several RemoteSources. |
| RemoteSourceCollection | Collection of RemoteSource objects. |
Interfaces
| Interface | Description |
|---|---|
| IEntityLoader | Interface supported by mappers to load entities to ObjectContext objects. |
| IEntityUpdater | Interface supported by mappers to update entities and references from ObjectContext objects. |
| ITransactional | Interface used for transactional purposes. |
Structures
| Structure | Description |
|---|---|
| RemoteSource | Structure representing a remote resource. |
Enumerations
| Enumeration | Description |
|---|---|
| PreloadFlags | Flags indicating what to load. |