TCustomEntityContext.Attach

The method is designed for attaching an entity instance to the data context and storing it in the object cache

Unit

Syntax

Remarks

The method attaches an entity instance created with TCustomEntityContext.CreateEntity to the data context and places it to the object cache. As a result of this method execution, several aims are reached:

• on subsequent calls to the same entity (e.g., using the TCustomEntityContext.GetEntity method), an instance saved in the cache will be returned, that eliminates re-accessing a database and significantly increases performance;
• there appears a possibility to perform modification operations for the entity instance: TCustomEntityContext.Delete, TCustomEntityContext.Save, TCustomEntityContext.Cancel,that will project instance modifications in appropriate database structures;
• the data context takes control of entity instance destruction on application shutdown, that eliminates the need to destroy objects manually.

Existence of separate TCustomEntityContext.CreateEntity and TCustomEntityContext.Attach methods is due to the check of uniqueness of the entity primary key value on saving it to the object cache, therefore it is expedient to use the method in case when the primary key value of an entity is unknown at the moment of its creation (or there is no confidence in its uniqueness).

If the primary key value of an entity is definitely known at the moment of its creation, then the TCustomEntityContext.CreateAttachedEntity method can be used.

See Also

• CreateEntity
• CreateAttachedEntity
• Delete
• Save
• Cancel
• TEntity