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Object-oriented Programming in C#
Specialization, Extension, and Inheritance
* Specialization of Classes
Specialization of Classes
The extension of class specialization
Example: Bank Accounts
Example: Bank Accounts in C#
Example: Geometric Shapes
Specialization of classes
The Principle of Substitution
* Extension of Classes
Extension of Classes
An example of simple extension
The intension of class extensions
* Inheritance in General
Inheritance
Interfaces to clients and subclasses
Visibility and Inheritance
Class hierarchies and Inheritance
Multiple inheritance
Problems with multiple inheritance
* Inheritance in C#
Class Inheritance in C#
The top of the class hierarchy
Methods in the class
Object
in C#
Inheritance and Constructors
Constructors and initialization order
Constructors and initialization order: Example
Visibility modifiers in C#
Inheritance of methods, properties, and indexers
Inheritance of methods: Example.
Overriding and Hiding in C#
Polymorphism. Static and dynamic types
Static and dynamic types in C#
Type test and type conversion in C#
Examples of type test and type conversion
Virtual methods in C#
Practical use of virtual methods in C#
Overriding the Equals method in a class
Upcasting and downcasting in C#
Upcasting and downcasting in C#
Inheritance and Variables
Overriding the Equals method in a class
It is tricky to do a correct overriding of the virtual
Equals
method in class
Object
Methods in class Object
Equality in C#
Equals in class Object
HashCode in class Object
Cases to deal with when redefining the
Equals
method:
Comparison with
null
(
false
)
Comparison with an object of a different type (
false
)
Comparison with
ReferenceEquals
(
true
)
Comparison of fields in two objects of the same type
Other rules when redefining
Equals
:
Must not lead to errors (no exceptions thrown)
The implemented equality should be
reflexive
,
symmetric
and
transitive
Additional work:
GetHashCode
should also be redefined in accordance with
Equals
If
o1.Equals(o2)
then
o1.GetHashCode() == o2.GetHashCode()
If you overload the
==
operator
Also overload
!=
Make sure that
o1 == o2
and
o1.Equals(o2)
return the same result
Equals and GetHashCode Methods in class BankAccount.
