Csharp 简明教程

C

C# 是一种面向对象编程语言。面向对象编程方法中，程序由各种通过操作相互交互的对象组成。对象可能采取的操作称为方法。相同种类对象被认为具有相同类型或属于同一类。

C# is an object-oriented programming language. In Object-Oriented Programming methodology, a program consists of various objects that interact with each other by means of actions. The actions that an object may take are called methods. Objects of the same kind are said to have the same type or, are said to be in the same class.

例如，我们考虑一个 Rectangle 对象。它具有诸如长度和宽度的属性。根据设计，它可能需要接受这些属性值、计算面积并显示详细信息的方法。

For example, let us consider a Rectangle object. It has attributes such as length and width. Depending upon the design, it may need ways for accepting the values of these attributes, calculating the area, and displaying details.

我们来看看 Rectangle 类的实现，并讨论 C# 基本语法 −

Let us look at implementation of a Rectangle class and discuss C# basic syntax −

using System;

namespace RectangleApplication {
   class Rectangle {

      // member variables
      double length;
      double width;

      public void Acceptdetails() {
         length = 4.5;
         width = 3.5;
      }
      public double GetArea() {
         return length * width;
      }
      public void Display() {
         Console.WriteLine("Length: {0}", length);
         Console.WriteLine("Width: {0}", width);
         Console.WriteLine("Area: {0}", GetArea());
      }
   }
   class ExecuteRectangle {
      static void Main(string[] args) {
         Rectangle r = new Rectangle();
         r.Acceptdetails();
         r.Display();
         Console.ReadLine();
      }
   }
}

编译并执行上述代码后，将产生以下结果 −

When the above code is compiled and executed, it produces the following result −

Length: 4.5
Width: 3.5
Area: 15.75

The using Keyword

任何 C# 程序中的第一条语句为

The first statement in any C# program is

using System;

using 关键字用于将命名空间包括在程序中。程序可以包括多个 using 语句。

The using keyword is used for including the namespaces in the program. A program can include multiple using statements.

The class Keyword

class 关键字用于声明类。

The class keyword is used for declaring a class.

Comments in C

注释用于解释代码。编译器会忽略注释条目。C# 程序中的多行注释以 /* 开始，并以 */ 结束，如下所示 −

Comments are used for explaining code. Compilers ignore the comment entries. The multiline comments in C# programs start with /* and terminates with the characters */ as shown below −

/* This program demonstrates
The basic syntax of C# programming
Language */

单行注释由“//”符号指示。例如：

Single-line comments are indicated by the '//' symbol. For example,

}//end class Rectangle

Member Variables

变量是类的属性或数据成员，用于存储数据。在前述程序中，Rectangle 类有两个名为 length 和 width 的成员变量。

Variables are attributes or data members of a class, used for storing data. In the preceding program, the Rectangle class has two member variables named length and width.

Member Functions

函数是执行特定任务的语句集。类的成员函数在类中声明。示例类 Rectangle 包含三个成员函数：AcceptDetails、GetArea 和 Display。

Functions are set of statements that perform a specific task. The member functions of a class are declared within the class. Our sample class Rectangle contains three member functions: AcceptDetails, GetArea and Display.

Instantiating a Class

在前述程序中，ExecuteRectangle 类包含 Main() 方法，并实例化 Rectangle 类。

In the preceding program, the class ExecuteRectangle contains the Main() method and instantiates the Rectangle class.

Identifiers

标识符是一个用于识别类、变量、函数或任何其他用户定义项的名称。在 C# 中命名类的基本规则如下 −

An identifier is a name used to identify a class, variable, function, or any other user-defined item. The basic rules for naming classes in C# are as follows −

A name must begin with a letter that could be followed by a sequence of letters, digits (0 - 9) or underscore. The first character in an identifier cannot be a digit.
It must not contain any embedded space or symbol such as? - + ! @ # % ^ & * ( ) [ ] { } . ; : " ' / and \. However, an underscore ( _ ) can be used.
It should not be a C# keyword.

C

关键字是预先定义为 C# 编译器的保留字。这些关键字不能用作标识符。但是，如果您想将这些关键字用作标识符，您可以在关键字前加上 @ 字符。

Keywords are reserved words predefined to the C# compiler. These keywords cannot be used as identifiers. However, if you want to use these keywords as identifiers, you may prefix the keyword with the @ character.

在 C# 中，一些标识符在代码上下文中具有特殊含义，例如 get 和 set 被称为上下文关键字。

In C#, some identifiers have special meaning in context of code, such as get and set are called contextual keywords.

下表列出了 C# 中的保留关键字和上下文关键字 -

The following table lists the reserved keywords and contextual keywords in C# −

Reserved Keywords

abstract

base

bool

break

byte

case

catch

char

checked

class

const

continue

decimal

default

delegate

double

else

enum

event

explicit

extern

false

finally

fixed

float

for

foreach

goto

implicit

in (generic modifier)

int

interface

internal

lock

long

namespace

new

null

object

operator

out

out (generic modifier)

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

volatile

while

Contextual Keywords

add

alias

ascending

descending

dynamic

from

get

global

group

into

join

let

orderby

partial (type)

partial (method)

remove

select

set