1. Martin Schray http://www.martinschray.com martin@martinschray.com
These materials where developed by Martin Schray. Please feel free to use and modify them for non-commercial purposes. If you find them useful or would like to suggest corrections or enhancements please drop me a note at
Martin Schray

2. VB .NET - Using Objects & basics about classes
Copyright © Martin Schray

3. VB .NET Classes Uses of a class
they can be used to define abstract data types
Data is protected or hidden inside a class
Class can be used to derive another class
New classes derived from existing class will inherit the data and methods already defined
public class MyClass
// class members
End Class

4. Declaring a class [attributes] [Class Modifiers] class ClassName
[inherits SuperClass]
[implements Interface]
//list of variables and methods declarations
End Class

5. Class Access Modifiers (page x)
Public
Optional. Public access. There are no restrictions on the use of public entities.
Private
Optional. Private access. A private entity is accessible only within its declaration context, including any nested entities.
Protected (only applies to class members)
Optional. Protected access. They are accessible only from within their own class or from a derived class. Protected access can be specified only on members of classes (including inner classes). It is not a superset of friend access.
Friend
Optional. Friend access. Only within the program that contains the entity declaration. Classes that do not specify an access modifier are declared as Friend by default.
Protected Friend
Optional. Entities declared with the Protected Friend modifiers have the union of protected and friend accessibility.

6. Other Class Modifiers Shadows (only applies to class members)
Optional. Indicates that this class shadows an identically named programming element in a base class. You can shadow any kind of declared element with any other kind. A shadowed element is unavailable in the derived class that shadows it
MustInherit
Optional. Indicates that non-shared members of the Class can only be accessed via derived classes. Instances of must-inherit classes cannot be created.
NotInheritable
Optional. Indicates that the Class is a class from which no further inheritance is allowed.

7. Class Modifiers
Only one modifier from each of the following groups can be used in a method declaration
public, private, friend, protected friend <empty – gives you the default of friend>
mustInherit, notIheritable

8. Class example public class point private x,y as integer
public sub move(dx as Integer, dy as integer)
x += dx;
y += dy;
End Sub
end class

9. Class Terms
All variables and functions of a class are called members of the class
Member functions of a class are also called methods of the class or simply methods
A object is not created until it is instantiated with the new keyword

10. Initializing Instance Variables
Instance variables are initialized automatically
Instance variables can also be assigned a default value

11. New Subroutine (Constructors)
New Methods are member functions which are automatically executed when a class is instantiated
The method has the name new
?New are invoked after initial default members are initialize
?No argument constructor is provided when no other constructor are provided

12. New Subroutine (Constructors)
There can multiple constructors (as long a signature differs)

13. Functions (return a value)
A class’s method typically contains the code that understands and manipulates an object’s state.
Syntax for method declaration follows
[ <attrlist> ] [{ Overloads | Overrides | Overridable | NotOverridable | MustOverride | Shadows | Shared }] [{ Public | Protected | Friend | Protected Friend | Private }] Function name[(arglist)] [ As type ] [ Implements interface.definedname ]
[ statements ] [ Exit Function ]
[ statements ]
End Function

14. Function Declaration Method declaration perform three main tasks:
determine who may call the method (public, private…)
determine what the method may receive as arguments (parameters)
determine what and if the method returns
VB. Net does not allow a variable number of arguments like c++

15. Subroutine (no return value)
Like a function, but with NO return value
[ <attrlist> ] [{ Overloads | Overrides | Overridable | NotOverridable | MustOverride | Shadows | Shared }] [{ Public | Protected | Friend | Protected Friend | Private }] Sub name [(arglist)] [ Implements interface.definedname ] [ statements ] [ Exit Sub ]
[ statements ]
End Sub

16. Sub Declaration Method declaration perform three main tasks:
determine who may call the method (public, private…)
determine what the method may receive as arguments (parameters)
NO RETURN TYPE
VB. Net does not allow a variable number of arguments like c++

17. Function and Sub Modifiers
Public
Optional. Public access. There are no restrictions on the accessibility of public procedures.
Protected
Optional. Protected access. They are accessible only from within their own class or from a derived class. Protected access can be specified only on members of classes. It is not a superset of friend access.
Friend
Optional. Procedures declared with the Friend keyword have friend access. They are accessible from within the program that contains their declaration and from anywhere else in the same assembly.
Protected Friend
Optional. Protected Friend keywords have the union of protected and friend access. They can be used by code in the same assembly, as well as by code in derived classes. Protected friend access can be specified only on members of classes.
Private
Optional. Private access. They are accessible only from within their declaration context, including from members of any nested types such as procedures.

18. Function & sub Modifiers
Overloads
Optional. This Sub procedure overloads one or more procedures defined with the same name in a base class. The argument list in this declaration must be different from the argument list of every overloaded procedure.
Overrides
Optional. Indicates that this Sub procedure overrides an identically named procedure in a base class.

19. Function and Sub Modifiers
Overridable
Optional. Indicates that this Sub procedure can be overridden by an identically named procedure in a derived class.
NotOverridable
Optional. Indicates that this Sub procedure cannot be overridden in a derived class.
MustOverride
Optional. Indicates that this Sub procedure is not implemented in this class and must be implemented in a derived class for that class to be creatable.
Shadows
Optional. A shadowed element is unavailable in the derived class that shadows it.

20. Method Modifiers
Only one modifier from each of the following groups can be used in a method declaration
public, protected, private, friend, protected friend<empty>
Overloads or shadows
Overrideable, noteoverridable, Mustoverride

21. Hello Class public class Hello ‘ class level variables go here
private shared count as interger = 0
private shared const msg as String = “I have been called this many times ”;
public sub new()
// constuctor
count++; // increment count by one
End Sub
public sub Message()
System.Console.writeln(msg & count);
end sub
End Class

22. Testing Classes Module Module1 Sub Main() Dim c As New FirstClass()
FirstClass.SharedTest()
c.test()
End Sub
End Module
Public Class FirstClass
Public Sub test()
System.Console.WriteLine("test")
Public Shared Sub SharedTest()
System.Console.WriteLine("Shared test")
End Class