C#C# Classes & Methods CS3260 Dennis A. Fairclough Version 1.1 Classes & Methods CS3260 Dennis A....

C#C#

Classes & Methods

CS3260

Dennis A. FaircloughVersion 1.1

Classes & Methods

CS3260

Dennis A. FaircloughVersion 1.1

C# Program StructureC# Program Structure

• Namespace(s)– Class(es)

• Method(s)– Statements

• Namespace(s)– Class(es)

• Method(s)– Statements

Copyright © 2010 by Dennis A. Fairclough all rights reserved. 2

namespace Program

{

static class A

{

static void Main( )

{

Console.WriteLine(“Hello”);

}

}

}

namespace Program

{

static class A

{

static void Main( )

{

Console.WriteLine(“Hello”);

}

}

}Copyright © 2010 by Dennis A. Fairclough all rights reserved. 3

NamespacesNamespaces• Global• System• User

– Separate– Cascaded

• namespace – keyword –• public implied

• Global• System• User

– Separate– Cascaded

• namespace – keyword –• public implied


Fully Qualified NameFully Qualified Name

• Uniquely identifies the namespace• i.e. System.Text.RegularExpressions

• Uniquely identifies the namespace• i.e. System.Text.RegularExpressions


NamespacesNamespaces

• Namespaces provide a hierarchical means of organizing C# programs and libraries. Namespaces contain types and other namespaces …

C# 3.0 Specification

• Scoping Mechanism

• Namespaces provide a hierarchical means of organizing C# programs and libraries. Namespaces contain types and other namespaces …


• Scoping MechanismCopyright © 2010 by Dennis A. Fairclough all rights reserved. 6

using Directive / Statementusing Directive / Statement• using – keyword –• using System; //directs compiler to use System namespace

using (TextWriter w) //statement

{

w.WriteLine(“Line One”);

}

• using – keyword –• using System; //directs compiler to use System namespace

using (TextWriter w) //statement

{

w.WriteLine(“Line One”);

}Copyright © 2010 by Dennis A. Fairclough all rights reserved. 7

Classes & ObjectsClasses & Objects• Classes are the most fundamental of C#’s types. A class

is a data structure that combines state (fields) and actions (methods and other function members) in a single unit. A class provides a definition for dynamically created instances of the class, also known as objects. Classes support inheritance and polymorphism, mechanisms whereby derived classes can extend and specialize base classes.


• Classes are the most fundamental of C#’s types. A class is a data structure that combines state (fields) and actions (methods and other function members) in a single unit. A class provides a definition for dynamically created instances of the class, also known as objects. Classes support inheritance and polymorphism, mechanisms whereby derived classes can extend and specialize base classes.



ClassesClasses• Instance class

– Instantiated as an object to be used

• Instance class with static members– class level for static members– instantiated for instance members

• static class– class level for members

• abstract class – Discuss later

• Instance class– Instantiated as an object to be used

• Instance class with static members– class level for static members– instantiated for instance members

• static class– class level for members

• abstract class – Discuss laterCopyright © 2010 by Dennis A. Fairclough all rights reserved. 9

Class MembersClass Members

• The members of a class are either static members, abstract members or instance members. Static members belong to classes, and instance members belong to objects (instances of classes). C# 3.0 Specification

• The members of a class are either static members, abstract members or instance members. Static members belong to classes, and instance members belong to objects (instances of classes). C# 3.0 Specification


Class MembersClass Members


Member DescriptionConstants Constant values associated with the classFields Variables of the classMethods Computations and actions that can be performed by the classProperties Actions associated with reading and writing named properties of the classIndexers Actions associated with indexing instances of the class like an arrayEvents Notifications that can be generated by the classOperators Conversions and expression operators supported by the classConstructors Actions required to initialize instances of the class or the class itselfDestructors Actions to perform before instances of the class are permanently discardedTypes Nested types declared by the class

AccessibilityAccessibility


Accessibility Meaningpublic Access not limitedprotected Access limited to this class or classes derived from this classinternal Access limited to this programprotected internal Access limited to this program or classes derived from this classprivate Access limited to this class

System.ObjectSystem.Object

• The MOST base class for any class• Provided by the compiler if you don’t• object or Object or System.Object

• The MOST base class for any class• Provided by the compiler if you don’t• object or Object or System.Object


Class ModifiersClass Modifiers

• abstract – Must be inherited from• sealed – Cannot be inherited from• static – Only static members• Contained class – A class declared in

containing class• Generic – Meta class

• abstract – Must be inherited from• sealed – Cannot be inherited from• static – Only static members• Contained class – A class declared in

containing class• Generic – Meta class


MethodsMethods• Method, function, procedure, other• Parameters – Zero or more• Method body• Local variables• Static or instance• virtual, override, new, abstract• Overloaded

• Method, function, procedure, other• Parameters – Zero or more• Method body• Local variables• Static or instance• virtual, override, new, abstract• Overloaded


Other MethodsOther Methods• Constructors• Properties• Indexers• Events• Operators• Destructors• Partial

• Constructors• Properties• Indexers• Events• Operators• Destructors• Partial Copyright © 2010 by Dennis A. Fairclough all rights reserved. 16

Method ParametersMethod Parameters

• Value• Reference• Output• Parameter Arrays

• Value• Reference• Output• Parameter Arrays


On and OnOn and On• Static• Instance• Virtual• Override/new• Sealed• Abstract• External• Partial• Extension• Overloaded• Generic

• Static• Instance• Virtual• Override/new• Sealed• Abstract• External• Partial• Extension• Overloaded• Generic


Method - WorkerMethod - Worker

• A method is a member that implements a computation or action that can be performed by an object or class. Static methods are accessed through the class. Instance methods are accessed through instances of the class.

• A method is a member that implements a computation or action that can be performed by an object or class. Static methods are accessed through the class. Instance methods are accessed through instances of the class.


Method ParametersMethod Parameters

• Methods have a (possibly empty) list of parameters, which represent values or variable references passed to the method, and a return type, which specifies the type of the value computed and returned by the method. A method’s return type is void if it does not return a value.

• Methods have a (possibly empty) list of parameters, which represent values or variable references passed to the method, and a return type, which specifies the type of the value computed and returned by the method. A method’s return type is void if it does not return a value.


Methods Pass ByMethods Pass By

• Value• Reference• out• param• etc.

• Value• Reference• out• param• etc.


Method SignaturesMethod Signatures

• The signature of a method must be unique in the class in which the method is declared. The signature of a method consists of the name of the method, the list of parameters (if any), modifiers, and types of its parameters. The signature of a method does not include the return type.

• The signature of a method must be unique in the class in which the method is declared. The signature of a method consists of the name of the method, the list of parameters (if any), modifiers, and types of its parameters. The signature of a method does not include the return type.


Parameters vs ArgumentsParameters vs Arguments

• Parameters are used to pass values or variable references to methods. The parameters of a method get their actual values from the arguments that are specified when the method is invoked. There are four kinds of parameters: value parameters, reference parameters, output parameters, and parameter arrays.

• Parameters are used to pass values or variable references to methods. The parameters of a method get their actual values from the arguments that are specified when the method is invoked. There are four kinds of parameters: value parameters, reference parameters, output parameters, and parameter arrays.


Method BodyMethod Body

• A method’s body specifies the statements to execute when the method is invoked.

• A method body can declare variables that are specific to the invocation of the method. Such variables are called local variables. A local variable declaration specifies a type name, a variable name, and possibly an initial value.

• A method’s body specifies the statements to execute when the method is invoked.

• A method body can declare variables that are specific to the invocation of the method. Such variables are called local variables. A local variable declaration specifies a type name, a variable name, and possibly an initial value.


Implicitly TypedImplicitly Typed

• When the local-variable-type is specified as var and no type named var is in scope, the declaration is an implicitly typed local variable declaration, whose type is inferred from the type of the associated initializer expression.

• When the local-variable-type is specified as var and no type named var is in scope, the declaration is an implicitly typed local variable declaration, whose type is inferred from the type of the associated initializer expression.


Local VariablesLocal Variables• Data Typing

– Signed Integer – sbyte, short, int, long– Unsigned Integer – byte, ushort, uint, ulong– Floating Point – float, double, decimal– Character – char– Boolen – bool– Implicit - var

• Data Typing– Signed Integer – sbyte, short, int, long– Unsigned Integer – byte, ushort, uint, ulong– Floating Point – float, double, decimal– Character – char– Boolen – bool– Implicit - var


KeywordsKeywords


abstract As base bool break

byte case catch char checked

class const continue decimal default

delegate do double else enum

event explicit extern false finally

fixed float for foreach goto

if implicit in int interface

internal is lock long namespace

new null object operator out

override params private protected public

readonly ref return sbyte sealed

short sizeof stackalloc static string

struct switch this throw true

try typeof uint ulong unchecked

unsafe ushort using virtual void

while

Contextual KeywordsContextual Keywords


add ascending by descending equals

from get global group in

into join let on orderby

partial remove select set value

var where yield

Contextual keywordsThe language also has contextual keywords, which, while recognized by the compiler, can still be used, unqualified, as identifiers. These are:

Literal SuffixesLiteral Suffixes


Category C# type Notes Example

F float float f = 1.0F;

D double double d = 1D;

M decimal decimal d = 1.0M;

U uint or ulong Combinable with L uint i = 1U;

L long or ulong Combinable with U ulong i = 1UL;

Floating Point ValuesFloating Point Values


Special value Double constant Float constant

NaN double.NaN float.NaN

+ double.PositiveInfinity float.PositiveInfinity

- double.NegativeInfinity float.NegativeInfinity

-0 -0.0 -0.0f


Character and string escape sequences

Char Meaning Value

\' Single quote 0x0027

\" Double quote 0x0022

\\ Backslash 0x005C

\0 Null 0x0000

\a Alert 0x0007

\b Backspace 0x0008

\f Form feed 0x000C

\n New line 0x000A

\r Carriage return 0x000D

\t Horizontal tab 0x0009

\v Vertical tab 0x000B

Date post:	12-Jan-2016
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C#C# Classes & Methods CS3260 Dennis A. Fairclough Version 1.1 Classes & Methods CS3260 Dennis A....

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