Inheritance
A class can inherit from another class to
extend or customize the original class. Inheriting from a class lets you
reuse the functionality in that class instead of building it from scratch.
A class can inherit from only a single class, but can itself be inherited
by many classes, thus forming a class hierarchy. In this example, we start
by defining a class called Asset
:
public class Asset { public string Name; }
Next, we define classes called Stock
and House
, which will inherit from Asset
. Stock
and House
get everything an Asset
has, plus any additional members that they
define:
public class Stock: Asset
// inherits from Asset { public long SharesOwned; } public class House: Asset
// inherits from Asset { public decimal Mortgage; }
Here’s how we can use these classes:
Stock msft = new Stock { Name="MSFT", SharesOwned=1000 }; Console.WriteLine (msft.Name); // MSFT Console.WriteLine (msft.SharesOwned); // 1000 House mansion = new House { Name="Mansion", Mortgage=250000 }; Console.WriteLine (mansion.Name); // Mansion Console.WriteLine (mansion.Mortgage); // 250000
The subclasses, Stock
and House
, inherit the Name
property from the base
class, Asset
.
Subclasses are also called derived classes.
Polymorphism
References are polymorphic. This means a variable of type x can refer to an object that subclasses x. For instance, consider the following method:
public static void Display (Asset asset) { System.Console.WriteLine (asset.Name); }
This method can display both a Stock
and a House ...
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