C # classes, objects, methods, properties (excerpt) thanks to the blog Park, thanks to the provider. Thank me Zhang Shuai brother.

C # classes, objects, methods, and properties in a detailed

First, related concepts:

1. Objects: Entities in the real world (objects of all things)

2. Class: A collection of objects with similar properties and methods

3, object-oriented Programming features: Package inheritance polymorphism

4. Three elements of an object: the attribute (what the object is), the method (what the object can do), the event (how the object responds)

☆ Interrelationships: Classes are abstractions of objects, objects are instances of classes, classes are abstract classifications, objects are concrete things.

For example, if the car is a class, a person's Mercedes-Benz is an object, the car's color quality is its properties, start, stop these actions can be defined as a vehicle method.

Ii. definition and grammar of classes

1. Define the class:

[Modifier] class name

{

Class Member

}

2. Class access modifier:public Internal

A) Public: accessible domain is the program where the access is located and any referenced program access is not restricted

Grammar:

public class class name

{

Class Member

}

b) Internal: Accessible domain definition in scope (default access modifier)

Grammar:

(internal) class name

{

Class Member

}

3. Class Members: data members and fields

A) Data members: Fields and Constants

Fields: Variables

Declaration: Type field Name

Cases:

public class Persion
{
public string name;
}

b) Method Member (method is the behavior of the class, tell us what the class can do,)

Example method:

Modifier return value type method name (parameter list)

{

Method body

}

Modifiers: such as: public, private, protected, internal

Return value type: If the method has no return value, use void

Cases:

public class EXAMPLE01//instance method

{

public void SayHello ()//define a method with no parameters and no return

{

Console.WriteLine ("Hello There")

}

static void Main ()

{

EXAMPLE01 obja=new Example01 ()

Obja.sayhello ()//Create object and Invoke method

}

}

static method:

Modifier static return value type method name (parameter list)//Add static keyword

{

Method body

}

Cases:

public class EXAMPLE01//instance method

{

public static void SayHello ()//define a static method

{

Console.WriteLine ("Hello There")

}

static void Main ()

{

Example01.sayhello ()//Do not need to create an object

}

}

☆ the difference between a static method and an instance method : A static method is only related to a class, it does not depend on the existence of an object, and an instance method is used after the object exists.

4. Access modifiers for members:public, private, protected, internal

A) public: publicly owned members

b) Private: Private Member

c) Protected: protection of Members

D) Internal: internal Members

usingSystem;usingSystem.Collections.Generic;usingSystem.Linq;usingSystem.Text;namespaceconsoleapplication2{ Public classEmployee {Private floatsum;  Public intDay ;  Public floatwage; //Define method output payroll information         Public voidShow () {sum= Day *wage; Console.WriteLine ("working time: {0}, daily wage: {1}, total wage: {2}", day,wage,sum); }    }    classProgram {Static voidMain (string[] args) {Employee Employee=NewEmployee (); Employee.day= -; Employee.wage= -; //Employee.sum: Cannot access because it is a private member//Invoke method Real wagesemployee.        Show (); }    }} 

Iii. instanced object: Keyword: new

Grammar:

Class object Name =new Class ();

usingSystem;usingSystem.Collections.Generic;usingSystem.Linq;usingSystem.Text; namespaceConsoleApplication1 { Public classCar {Private stringCarname; Private stringCartype; Private intPrice ;  Public stringCarname {Get{returnCarname;} Set{Carname =value;} }          Public stringCartype {Get{returnCartype;} Set{Cartype =value;} }                  Public intPrice {Get{returnPrice ;} Set{Price =value;} }            Public voidaction () {Console.WriteLine ("a car named {0}, the model number is {1}, the price is: {2}", Carname,cartype,price); }               }       //create an instance and Access fields and methods    classProgram {Static voidMain (string[] args) {             //create an instance of the car classCar vehicle =Newcar (); //Assigning a value to an instanceVehicle. Carname ="Mercedes"; Vehicle. Cartype="XZ001"; Vehicle. Price=1000000; //Calling Methodsvehicle.action (); }     } }

Iv. attributes

1.

A) concept: a member of a field used to access a class

b) attribute use: ensure data security, data validation

2. Statement:

Access modifier data Type property name

{

Get{return field;} Read accessor, through which the external user can read the value of the property

set{field =value;} Write accessor, through which the external user can assign a value to a property, the value entered by the user is stored in the value keyword, and the input value can be verified

}

Cases:

public class Student

{

private int age; Private fields to prevent direct user access

public int Age

{

Get{return age;} Used to read the value of age

Set

{

if ((value>=18) && (value<=45))

Age=value; Assign to age and verify

Else

age=18;

}

}

}

3. Special attributes:

A) Read-only properties:

Public Data Type property name

{

Get{return field;}

}

b) Automatic attributes:

Public data Type property name {Get;set;}

V. Parameters of the method

1. Value parameter: pass by value

2. Reference parameter: Pass the address of the argument in memory to the method, pass it by address

3. Output parameters: Pass back a result from the method

Keywords: out

4, array parameter: The parameter is only allowed to be a set of arrays, when the method parameter with the params keyword, is the method with the array type parameter (using reference pass)

C # classes, objects, methods, properties (excerpt) thanks to the blog Park, thanks to the provider. Thank me Zhang Shuai brother.