C++.NET与C#的编码区别 ,vb.net与c#的语法比较

本文只讨论C++.NET与C#的编码区别,其理论区别请参考相关书籍.

1. 命名空间引用方法

C# 通过命名空间后跟"."来引用.

C++.NET 通过命名空间后跟"::"来引用

如: (c#)System.Data . (c++.net) System::Data

2.生成一个窗体的实例并显示出来

c++.net:
//通过指针操作

frmAbout* frm = new frmAbout();

frm->ShowDialog(this);

C#:

frmAbout frm = new frmAbout(); //生成对象的实例

frm.ShowDialog(this);

3.程序的入口点

c++.net

一个应用程序必须而且只能有一个CWinApp派生类的对象,并且只能由该对象来调

用WinMain()函数。这也对应着一个应用程序只有一个惟一的入口.

如:

[System::STAThreadAttribute]

void __stdcall WinMain()

{

Application::Run(new frmLogin());

}

WinMain函数在调用InitInstance进行初始化完毕后，就调用函数处理消息循环。

Run函数作为一个循环函数，主要进行消息的处理:Run函数不断地查询应用程序的消

息队列，一旦有消息出现就将其发回给Windows,并由Windows再来调用处理该消息的窗口

函数，而窗口则是隐藏在应用程序框架类内部的。当消息队列中没有消息时（大多数的时

候是这种情况）,Run函数就会调用OnIdle函数，从而做一些应用程序框架类或用户在程序

空闲时所要做的工作。
如果既没有消息又没有空闲工作要做,那么应用程序就一直处于等待状态.
当应用程序关闭时,Run函数就会调用ExitInstance函数,做一些退出前的处理工作.

C#也如此

如:

// <summary>

/// 应用程序的主入口点。

/// </summary>

[STAThread]

static void Main()

{

Application.Run(new frmLogin());

}

4.设置(或获取)窗体和相关组件的属性

(下面的实例均基于相同的命名空间)

c++.net

this->BackColor =System::Drawing::Color::Gold ;

this->textBox1->Text =this->BackColor.ToString();

this->pictureBox1->BackColor =System::Drawing::Color::Red ;

    C#
        this.BackColor=System.Drawing.Color.Gold; //获取或设置本窗体的属性用 this.
        this.textBox1.Text =this.BackColor.ToString();
        Form2 frm2=new Form2();

frm2.BackColor=System.Drawing.Color.Gold; //获取或设置新实例窗体的属性用新实例名.

frm2.ShowDialog(this) ;

frm2.Close();

this.pictureBox1.BackColor = System.Drawing.Color.Red ;

5 .C#和VB.net的语法比较

C#和VB.net的语法比较

Comments

VB.NET

'Single line only

Rem Single line only

// Single line

/* Multiple

line */

/// XML comments on single line

/** XML comments on multiple lines */

Data Types

VB.NET

'Value Types

Boolean

Byte

Char (example: "A")

Short, Integer, Long

Single, Double

Decimal

Date

'Reference Types

Object

String

Dim x As Integer

System.Console.WriteLine(x.GetType())

System.Console.WriteLine(TypeName(x))

'Type conversion

Dim d As Single = 3.5

Dim i As Integer = CType (d, Integer)

i = CInt (d)

i = Int(d)

//Value Types

bool

byte, sbyte

char (example: 'A')

short, ushort, int, uint, long, ulong

float, double

decimal

DateTime

//Reference Types

object

string

int x;

Console.WriteLine(x.GetType())

Console.WriteLine(typeof(int))

//Type conversion

float d = 3.5;

int i = (int) d

Constants

VB.NET

Const MAX_AUTHORS As Integer = 25

ReadOnly MIN_RANK As Single = 5.00

const int MAX_AUTHORS = 25;

readonly float MIN_RANKING = 5.00;

Enumerations

VB.NET

Enum Action

Start

'Stop is a reserved word

[Stop]

Rewind

Forward

End Enum

Enum Status

Flunk = 50

Pass = 70

Excel = 90

End Enum

Dim a As Action = Action.Stop

If a <> Action.Start Then _

'Prints "Stop is 1"

System.Console.WriteLine(a.ToString & " is " & a)

'Prints 70

System.Console.WriteLine(Status.Pass)

'Prints Pass

System.Console.WriteLine(Status.Pass.ToString())

enum Action {Start, Stop, Rewind, Forward};

enum Status {Flunk = 50, Pass = 70, Excel = 90};

Action a = Action.Stop;

if (a != Action.Start)

//Prints "Stop is 1"

System.Console.WriteLine(a + " is " + (int) a);

// Prints 70

System.Console.WriteLine((int) Status.Pass);

// Prints Pass

System.Console.WriteLine(Status.Pass);

Operators

VB.NET

'Comparison

= < > <= >= <>

'Arithmetic

+ - * /

Mod

(integer division)

^ (raise to a power)

'Assignment

= += -= *= /= = ^= <<= >>= &=

'Bitwise

And AndAlso Or OrElse Not << >>

'Logical

And AndAlso Or OrElse Not

'String Concatenation

//Comparison

== < > <= >= !=

//Arithmetic

+ - * /

% (mod)

/ (integer division if both operands are ints)

Math.Pow(x, y)

//Assignment

= += -= *= /= %= &= |= ^= <<= >>= ++ --

//Bitwise

& | ^ ~ << >>

//Logical

&& || !

//String Concatenation

Choices

VB.NET

greeting = IIf(age < 20, "What's up?", "Hello")

'One line doesn't require "End If", no "Else"

If language = "VB.NET" Then langType = "verbose"

'Use: to put two commands on same line

If x <> 100 And y < 5 Then x *= 5 : y *= 2

'Preferred

If x <> 100 And y < 5 Then

x *= 5

y *= 2

End If

'or to break up any long single command use _

If henYouHaveAReally < longLine And _

itNeedsToBeBrokenInto2 > Lines Then _

UseTheUnderscore(charToBreakItUp)

If x > 5 Then

x *= y

ElseIf x = 5 Then

x += y

ElseIf x < 10 Then

x -= y

Else

x /= y

End If

'Must be a primitive data type

Select Case color

Case "black", "red"

r += 1

Case "blue"

b += 1

Case "green"

g += 1

Case Else

other += 1

End Select

greeting = age < 20 ? "What's up?" : "Hello";

if (x != 100 && y < 5)

{

// Multiple statements must be enclosed in {}

x *= 5;

y *= 2;

}

if (x > 5)

x *= y;

else if (x == 5)

x += y;

else if (x < 10)

x -= y;

else

x /= y;

//Must be integer or string

switch (color)

{

case "black":

case "red": r++;

break;

case "blue"

break;

case "green": g++;

break;

default: other++;

break;

}

Loops

VB.NET

'Pre-test Loops:

While c < 10

c += 1

End While Do Until c = 10

c += 1

Loop

'Post-test Loop:

Do While c < 10

c += 1

Loop

For c = 2 To 10 Step 2

System.Console.WriteLine(c)

'Array or collection looping

Dim names As String() = {"Steven", "SuOk", "Sarah"}

For Each s As String In names

System.Console.WriteLine(s)

//Pre-test Loops: while (i < 10)

i++;

for (i = 2; i < = 10; i += 2)

System.Console.WriteLine(i);

//Post-test Loop:

i++;

while (i < 10);

// Array or collection looping

string[] names = {"Steven", "SuOk", "Sarah"};

foreach (string s in names)

System.Console.WriteLine(s);

Arrays

VB.NET

Dim nums() As Integer = {1, 2, 3}

For i As Integer = 0 To nums.Length - 1

Console.WriteLine(nums(i))

'4 is the index of the last element, so it holds 5 elements

Dim names(4) As String

names(0) = "Steven"

'Throws System.IndexOutOfRangeException

names(5) = "Sarah"

'Resize the array, keeping the existing

'values (Preserve is optional)

ReDim Preserve names(6)

Dim twoD(rows-1, cols-1) As Single

twoD(2, 0) = 4.5

Dim jagged()() As Integer = { _

New Integer(4) {}, New Integer(1) {}, New Integer(2) {} }

jagged(0)(4) = 5

int[] nums = {1, 2, 3};

for (int i = 0; i < nums.Length; i++)

Console.WriteLine(nums[i]);

// 5 is the size of the array

string[] names = new string[5];

names[0] = "Steven";

// Throws System.IndexOutOfRangeException

names[5] = "Sarah"

// C# can't dynamically resize an array.

//Just copy into new array.

string[] names2 = new string[7];

// or names.CopyTo(names2, 0);

Array.Copy(names, names2, names.Length);

float[,] twoD = new float[rows, cols];

twoD[2,0] = 4.5;

int[][] jagged = new int[3][] {

new int[5], new int[2], new int[3] };

jagged[0][4] = 5;

Functions

VB.NET

'Pass by value (in, default), reference

'(in/out), and reference (out)

Sub TestFunc(ByVal x As Integer, ByRef y As Integer,

ByRef z As Integer)

x += 1

y += 1

z = 5

End Sub

'c set to zero by default

Dim a = 1, b = 1, c As Integer

TestFunc(a, b, c)

System.Console.WriteLine("{0} {1} {2}", a, b, c) '1 2 5

'Accept variable number of arguments

Function Sum(ByVal ParamArray nums As Integer()) As Integer

Sum = 0

For Each i As Integer In nums

Sum += i

End Function 'Or use a Return statement like C#

Dim total As Integer = Sum(4, 3, 2, 1) 'returns 10

'Optional parameters must be listed last

'and must have a default value

Sub SayHello(ByVal name As String,

Optional ByVal prefix As String = "")

System.Console.WriteLine("Greetings, " & prefix

& " " & name)

End Sub

SayHello("Steven", "Dr.")

SayHello("SuOk")

// Pass by value (in, default), reference

//(in/out), and reference (out)

void TestFunc(int x, ref int y, out int z) {

x++;

y++;

z = 5;

}

int a = 1, b = 1, c; // c doesn't need initializing

TestFunc(a, ref b, out c);

System.Console.WriteLine("{0} {1} {2}", a, b, c); // 1 2 5

// Accept variable number of arguments

int Sum(params int[] nums) {

int sum = 0;

foreach (int i in nums)

sum += i;

return sum;

}

int total = Sum(4, 3, 2, 1); // returns 10

/* C# doesn't support optional arguments/parameters.

Just create two different versions of the same function. */

void SayHello(string name, string prefix) {

System.Console.WriteLine("Greetings, "
+ prefix + " " + name);

}

void SayHello(string name) {

SayHello(name, "");

}

Exception Handling

VB.NET

'Deprecated unstructured error handling

On Error GoTo MyErrorHandler

...

MyErrorHandler: System.Console.WriteLine(Err.Description)

Dim ex As New Exception("Something has really gone wrong.")

Throw ex

Try

y = 0

x = 10 / y

Catch ex As Exception When y = 0 'Argument and When is optional

System.Console.WriteLine(ex.Message)

Finally

DoSomething()

End Try

Exception up = new Exception("Something is really wrong.");

throw up; // ha ha

try{

y = 0;

x = 10 / y;

}

catch (Exception ex) { //Argument is optional, no "When" keyword

Console.WriteLine(ex.Message);

}

finally{

// Do something

}

Namespaces

VB.NET

Namespace ASPAlliance.DotNet.Community

...

End Namespace

'or

Namespace ASPAlliance

Namespace DotNet

Namespace Community

...

End Namespace

Imports ASPAlliance.DotNet.Community

namespace ASPAlliance.DotNet.Community {

...

}

// or

namespace ASPAlliance {

namespace DotNet {

namespace Community {

...

}

using ASPAlliance.DotNet.Community;

Classes / Interfaces

VB.NET

'Accessibility keywords

Public

Private

Friend

Protected

Protected Friend

Shared

'Inheritance

Class Articles

Inherits Authors

...

End Class

'Interface definition

Interface IArticle

...

End Interface

'Extending an interface

Interface IArticle

Inherits IAuthor

...

End Interface

'Interface implementation</span>

Class PublicationDate

Implements</strong> IArticle, IRating

...

End Class

//Accessibility keywords

public

private

internal

protected

protected internal

static

//Inheritance

class Articles: Authors {

...

}

//Interface definition

interface IArticle {

...

}

//Extending an interface

interface IArticle: IAuthor {

...

}

//Interface implementation

class PublicationDate: IArticle, IRating {

...

}

Constructors / Destructors

VB.NET

Class TopAuthor

Private _topAuthor As Integer

Public Sub New()

_topAuthor = 0

End Sub

Public Sub New(ByVal topAuthor As Integer)

Me._topAuthor = topAuthor

End Sub

Protected Overrides Sub Finalize()

'Desctructor code to free unmanaged resources

MyBase.Finalize()

End Sub

End Class

class TopAuthor {

private int _topAuthor;

public TopAuthor() {

_topAuthor = 0;

}

public TopAuthor(int topAuthor) {

this._topAuthor= topAuthor

}

~TopAuthor() {

// Destructor code to free unmanaged resources.

// Implicitly creates a Finalize method

}

Objects

VB.NET

Dim author As TopAuthor = New TopAuthor

With author

.Name = "Steven"

.AuthorRanking = 3

End With

author.Rank("Scott")

author.Demote() 'Calling Shared method

'or

TopAuthor.Rank()

Dim author2 As TopAuthor = author 'Both refer to same object

author2.Name = "Joe"

System.Console.WriteLine(author2.Name) 'Prints Joe

author = Nothing 'Free the object

If author Is Nothing Then _

author = New TopAuthor

Dim obj As Object = New TopAuthor

If TypeOf obj Is TopAuthor Then _

System.Console.WriteLine("Is a TopAuthor object.")

TopAuthor author = new TopAuthor();

//No "With" construct

author.Name = "Steven";

author.AuthorRanking = 3;

author.Rank("Scott");

TopAuthor.Demote() //Calling static method

TopAuthor author2 = author //Both refer to same object

author2.Name = "Joe";

System.Console.WriteLine(author2.Name) //Prints Joe

author = null //Free the object

if (author == null)

author = new TopAuthor();

Object obj = new TopAuthor();

if (obj is TopAuthor)

SystConsole.WriteLine("Is a TopAuthor object.");

Structs

VB.NET

Structure AuthorRecord

Public name As String

Public rank As Single

Public Sub New(ByVal name As String, ByVal rank As Single)

Me.name = name

Me.rank = rank

End Sub

End Structure

Dim author As AuthorRecord = New AuthorRecord("Steven", 8.8)

Dim author2 As AuthorRecord = author

author2.name = "Scott"

System.Console.WriteLine(author.name) 'Prints Steven

System.Console.WriteLine(author2.name) 'Prints Scott

struct AuthorRecord {

public string name;

public float rank;

public AuthorRecord(string name, float rank) {

this.name = name;

this.rank = rank;

}

AuthorRecord author = new AuthorRecord("Steven", 8.8);

AuthorRecord author2 = author

author.name = "Scott";

SystemConsole.WriteLine(author.name); //Prints Steven

System.Console.WriteLine(author2.name); //Prints Scott

Properties

VB.NET

Private _size As Integer

Public Property Size() As Integer

Get

Return _size

End Get

Set (ByVal Value As Integer)

If Value < 0 Then

_size = 0

Else

_size = Value

End If

End Set

End Property

foo.Size += 1

private int _size;

public int Size {

get {

return _size;

}

set {

if (value < 0)

_size = 0;

else

_size = value;

}

foo.Size++;

Delegates / Events

VB.NET

Delegate Sub MsgArrivedEventHandler(ByVal message

As String)

Event MsgArrivedEvent As MsgArrivedEventHandler

'or to define an event which declares a

'delegate implicitly

Event MsgArrivedEvent(ByVal message As String)

AddHandler MsgArrivedEvent, AddressOf My_MsgArrivedCallback

'Won't throw an exception if obj is Nothing

RaiseEvent MsgArrivedEvent("Test message")

RemoveHandler MsgArrivedEvent, AddressOf My_MsgArrivedCallback

Imports System.Windows.Forms

'WithEvents can't be used on local variable

Dim WithEvents MyButton As Button

MyButton = New Button

Private Sub MyButton_Click(ByVal sender As System.Object, _

ByVal e As System.EventArgs) Handles MyButton.Click

MessageBox.Show(Me, "Button was clicked", "Info", _

MessageBoxButtons.OK, MessageBoxIcon.Information)

End Sub

delegate void MsgArrivedEventHandler(string message);

event MsgArrivedEventHandler MsgArrivedEvent;

//Delegates must be used with events in C#

MsgArrivedEvent += new MsgArrivedEventHandler

(My_MsgArrivedEventCallback);

//Throws exception if obj is null

MsgArrivedEvent("Test message");

MsgArrivedEvent -= new MsgArrivedEventHandler

(My_MsgArrivedEventCallback);

using System.Windows.Forms;

Button MyButton = new Button();

MyButton.Click += new System.EventHandler(MyButton_Click);

private void MyButton_Click(object sender,
System.EventArgs e) {

MessageBox.Show(this, "Button was clicked", "Info",

MessageBoxButtons.OK, MessageBoxIcon.Information);

}

Console I/O

VB.NET

'Special character constants

vbCrLf, vbCr, vbLf, vbNewLine

vbNullString

vbTab

vbBack

vbFormFeed

vbVerticalTab

Chr(65) 'Returns 'A'

System.Console.Write("What's your name? ")

Dim name As String = System.Console.ReadLine()

System.Console.Write("How old are you? ")

Dim age As Integer = Val(System.Console.ReadLine())

System.Console.WriteLine("{0} is {1} years old.", name, age)

'or

System.Console.WriteLine(name & " is " & age & " years old.")

Dim c As Integer

c = System.Console.Read() 'Read single char

System.Console.WriteLine(c) 'Prints 65 if user enters "A"

//Escape sequences

n, r

Convert.ToChar(65)
//Returns 'A' - equivalent to Chr(num) in VB

// or

(char) 65

System.Console.Write("What's your name? ");

string name = SYstem.Console.ReadLine();

System.Console.Write("How old are you? ");

int age = Convert.ToInt32(System.Console.ReadLine());

System.Console.WriteLine("{0} is {1} years old.",
name, age);

//or

System.Console.WriteLine(name + " is " +
age + " years old.");

int c = System.Console.Read(); //Read single char

System.Console.WriteLine(c);
//Prints 65 if user enters "A"

File I/O

VB.NET

Imports System.IO

'Write out to text file

Dim writer As StreamWriter = File.CreateText

("c:myfile.txt")

writer.WriteLine("Out to file.")

writer.Close()

'Read all lines from text file

Dim reader As StreamReader = File.OpenText

("c:myfile.txt")

Dim line As String = reader.ReadLine()

While Not line Is Nothing

Console.WriteLine(line)

line = reader.ReadLine()

End While

reader.Close()

'Write out to binary file

Dim str As String = "Text data"

Dim num As Integer = 123

Dim binWriter As New BinaryWriter(File.OpenWrite

("c:myfile.dat"))

binWriter.Write(str)

binWriter.Write(num)

binWriter.Close()

'Read from binary file

Dim binReader As New BinaryReader(File.OpenRead

("c:myfile.dat"))

str = binReader.ReadString()

num = binReader.ReadInt32()

binReader.Close()

using System.IO;

//Write out to text file

StreamWriter writer = File.CreateText

("c:myfile.txt");

writer.WriteLine("Out to file.");

writer.Close();

//Read all lines from text file

StreamReader reader = File.OpenText

("c:myfile.txt");

string line = reader.ReadLine();

while (line != null) {

Console.WriteLine(line);

line = reader.ReadLine();

}

reader.Close();

//Write out to binary file

string str = "Text data";

int num = 123;

BinaryWriter binWriter = new BinaryWriter(File.OpenWrite

("c:myfile.dat"));

binWriter.Write(str);

binWriter.Write(num);

binWriter.Close();

//Read from binary file

BinaryReader binReader = new BinaryReader(File.OpenRead

("c:myfile.dat"));

str = binReader.ReadString();

num = binReader.ReadInt32();

binReader.Close();

未完侍续