Inheritance

Introduction

Any database object can inherit from any other database object. The Database attribute is inherited from base- to subclasses. Hence, any class that directly or indirectly inherits a class with the Database attribute becomes a database class.

Example

In this example, both PrivateCustomer and CorporateCustomer become database classes due to them inheriting Customer:

[Database]
public class Customer
{
   public string Name { get; set; }
}

public class PrivateCustomer : Customer
{
   public string Gender { get; set; }
}

public class CorporateCustomer : Customer
{
   public string VatNumber { get; set; }
}

The table Customer will contain all PrivateCustomers and all CorporateCustomers. So if there is a private customer called "Goldman, Carl" and a corporate customer called "Goldman Sachs", the result of SELECT C FROM Customer c will contain both of them.

Base Classes

A base class contains all instances of all derived classes in addition to the instances with the its own exact type.

SELECT C FROM Customer C WHERE Name LIKE 'Goldman%'

Returns [ { Name:"Goldman Sachs" }, { Name:"Goldman, Carl" } ]

Derived classes

SELECT C FROM PrivateCustomer C WHERE Name LIKE 'Goldman%'

Returns [{ Name:"Goldman, Carl", Gender:"Male" }]

SELECT C FROM CorporateCustomer C WHERE Name LIKE 'Goldman%'

Returns [{ Name:"Goldman Sachs", VatNumber:"1234" } ]

Inheriting From Non-Database Classes

A database class cannot inherit from a class that's not a database class. This will throw an error when the application is weaved.

It's also not possible to cast a non-database class to a database class.