ADO.Net Entity Framework

POCO Proxy is a runtime proxy class of POCO entity. POCO entity becomes POCO Proxy entity if it meets certain requirements to enable lazy loading proxy and instant change tracking. It adds some methods at runtime to your POCO class which does instant change tracking and lazy loading stuff.

POCO entity should meet the following requirement to become POCO proxy:

A custom data class must be declared with public access.

A custom data class must not be sealed (NotInheritable in Visual Basic)

A custom data class must not be abstract (MustInherit in Visual Basic).

A custom data class must have a public or protected constructor that does not have parameters.

The class cannot implement the IEntityWithChangeTracker or IEntityWithRelationships interfaces because the proxy classes implement these interfaces.

The ProxyCreationEnabled option must be set to true.

Each navigation property must be declared as public, virtual

A defining query allows you to execute a native SQL statement that is specified in the DefiningQuery element in the EntitySet element in the SSDL.

A defining query is commonly used to provide functionality similar to that provided by a database view, but this native SQL statement will be in the .edmx file, not in the database. The entityset in CSDL is used to surface data exposed by the defining query.

So here, we will see how we can execute same SQL using DifiningQuery which we used in database view in previous chapter and get the same functionality as database view.

We will perform following three steps to create and use DefiningQuery:

Add DefiningQuery in SSDL

Add EntitySet in CSDL

Mapping between Conceptual and Storage EntitySets