vb和C#的区别

Imports System

Namespace Hello
Class HelloWorld
Overloads Shared SubMain(ByVal args() As String)
Dim name As String = "VB.NET"

'See if an argument was passed from the command line
If args.Length = 1 Then name = args(0)

Console.WriteLine("Hello," & name & "!")
End Sub
End Class
End Namespace

using System;

namespace Hello {
public class HelloWorld {
public static voidMain(string[] args) {
string name = "C#";

// See if an argument was passed from the command line
if (args.Length == 1)
name = args[0];

Console.WriteLine("Hello," + name + "!");
}
}
}

' Single line only
RemSingle line only

// Single line
/* Multiple
line */
/// XML comments on single line
/** XML comments on multiple lines */

Value Types
Boolean
Byte
Char(example: "A"c)
Short,Integer,Long
Single,Double
Decimal
Date

Reference Types
Object
String

DimxAsInteger
Console.WriteLine(x.GetType())' Prints System.Int32
Console.WriteLine(GetType(Integer))' Prints System.Int32
Console.WriteLine(TypeName(x))' Prints Integer

' Type conversion
Dim d As Single = 3.5
Dim i As Integer =CType(d,Integer)' set to 4 (Banker's rounding)
i =CInt(d)' same result as CType
i =Int(d)' set to 3 (Int function truncates the decimal)

Value Types
bool
byte,sbyte
char(example: 'A')
short,ushort,int,uint,long,ulong
float,double
decimal
DateTime(not a built-in C# type)

Reference Types
object
string

int x;
Console.WriteLine(x.GetType());// Prints System.Int32
Console.WriteLine(typeof(int));// Prints System.Int32
Console.WriteLine(x.GetType().Name);// prints Int32

// Type conversion
float d = 3.5f;
int i =(int)d;// set to 3 (truncates decimal)

ConstMAX_STUDENTSAsInteger = 25

' Can set to a const or var; may be initialized in a constructor
ReadOnlyMIN_DIAMETERAsSingle = 4.93

constint MAX_STUDENTS = 25;

// Can set to a const or var; may be initialized in a constructor
readonlyfloat MIN_DIAMETER = 4.93f;

EnumAction
Start
[Stop]' Stop is a reserved word
Rewind
Forward
End Enum

EnumStatus
Flunk = 50
Pass = 70
Excel = 90
End Enum

Dim a As Action = Action.Stop
If a <> Action.Start Then _
Console.WriteLine(a.ToString & " is " & a)' Prints "Stop is 1"

Console.WriteLine(Status.Pass)' Prints 70
Console.WriteLine(Status.Pass.ToString())' Prints Pass

enumAction {Start,Stop,Rewind,Forward};
enumStatus {Flunk = 50,Pass = 70,Excel = 90};

Action a = Action.Stop;
if (a != Action.Start)
Console.WriteLine(a + " is " + (int) a);// Prints "Stop is 1"

Console.WriteLine((int) Status.Pass);// Prints 70
Console.WriteLine(Status.Pass);// Prints Pass

Comparison
= < > <= >= <>

Arithmetic
+ - * /
Mod
"(integer division)
^(raise to a power)

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

Bitwise
And Or Not << >>

Logical
AndAlso OrElse And Or Xor Not

Note:AndAlso and OrElse perform short-circuit logical evaluations

String Concatenation
& +

Comparison
== < > <= >= !=

Arithmetic
+ - * /
%(mod)
/(integer division if both operands are ints)
Math.Pow(x,y)

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

Bitwise
& | ^ ~ << >>

Logical
&& || & | ^ !

Note:&& and || perform short-circuit logical evaluations

String Concatenation
+

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

' One line doesn't require "End If"
Ifage < 20Thengreeting = "What's up?"
Ifage < 20Thengreeting = "What's up?"Elsegreeting = "Hello"

' Use : to put two commands on same line
Ifx <> 100 And y < 5Thenx *= 5:y *= 2

' Preferred
Ifx <> 100 And y < 5Then
x *= 5
y *= 2
End If

' To break up any long single line use _
IfwhenYouHaveAReally < longLine And _
itNeedsToBeBrokenInto2 > LinesThen_
UseTheUnderscore(charToBreakItUp)

'Ifx > 5Then
x *= y
ElseIfx = 5Then
x += y
ElseIfx < 10Then
x -= y
Else
x /= y
End If

Select Casecolor' Must be a primitive data type
Case"pink","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(age < 20)
greeting = "What's up?";
else
greeting = "Hello";

// Multiple statements must be enclosed in {}
if(x != 100 && y < 5) {
x *= 5;
y *= 2;
}

No need for _ or : since ; is used to terminate each statement.

if(x > 5)
x *= y;
elseif (x == 5)
x += y;
elseif (x < 10)
x -= y;
else
x /= y;

// Every case must end with break or goto case
switch(color) {// Must be integer or string
case"pink":
case"red": r++;break;
case"blue": b++;break;
case"green": g++;break;
default: other++;break;// break necessary on default
}

' Array or collection looping
Dim names As String() = {"Fred","Sue","Barney"}
For Eachs As StringInnames
Console.WriteLine(s)
Next

' Breaking out of loops
Dim i As Integer = 0
While (True)
If (i = 5) ThenExit While
i += 1
End While

' Continue to next iteration
For i = 0 To 4
If i < 4 ThenContinue For
Console.WriteLine(i)' Only prints 4
Next

Pre-test Loops:

// no "until" keyword
while(c < 10)
c++;

for(c = 2; c <= 10; c += 2)
Console.WriteLine(c);

Post-test Loop:

do
c++;
while(c < 10);



// Array or collection looping
string[] names = {"Fred","Barney"};
foreach(string sinnames)
Console.WriteLine(s);

// Breaking out of loops
int i = 0;
while (true) {
if (i == 5)
break;
i++;
}

// Continue to next iteration
for (i = 0; i < 5; i++) {
if (i < 4)
continue;
Console.WriteLine(i);// Only prints 4
}

Dim nums()As Integer = {1,2,3}
For i As Integer = 0 To nums.Length - 1
Console.WriteLine(nums(i))
Next

' 4 is the index of the last element,so it holds 5 elements
Dim names(4) As String
names(0) = "David"
names(5) = "Bobby"' Throws System.IndexOutOfRangeException

' Resize the array,keeping the existing values (Preserve is optional)
ReDim Preservenames(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 = {1,3};
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] = "David";
names[5] = "Bobby";// Throws System.IndexOutOfRangeException


// C# can't dynamically resize an array. Just copy into new array.
string[] names2 = new string[7];
Array.Copy(names,names2,names.Length);// or names.CopyTo(names2,0);

float[,]twoD = new float[rows,cols];
twoD[2,0] = 4.5f;

int[][]jagged = new int[3][] {
new int[5],new int[2],new int[3] };
jagged[0][4] = 5;

' Pass by value (in,default),reference (in/out),and reference (out)
SubTestFunc(ByValx As Integer,ByRefy As Integer,ByRefz As Integer)
x += 1
y += 1
z = 5
End Sub

Dim a = 1,b = 1,c As Integer' c set to zero by default
TestFunc(a,b,c)
Console.WriteLine("{0} {1} {2}",a,c)' 1 2 5

' Accept variable number of arguments
FunctionSum(ByValParamArraynumsAsInteger()) As Integer
Sum = 0
For Each i As Integer In nums
Sum += i
Next
End Function' Or use Return statement like C#

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

' Optional parameters must be listed last and must have a default value
SubSayHello(ByVal name As String,OptionalByVal prefix As String = "")
Console.WriteLine("Greetings," & prefix & " " & name)
End Sub

SayHello("Strangelove","Dr.")
SayHello("Madonna")

// Pass by value (in,and reference (out)
void TestFunc(int x,refint y,outint z) {
x++;
y++;
z = 5;
}

int a = 1,c;// c doesn't need initializing
TestFunc(a,refb,outc);
Console.WriteLine("{0} {1} {2}",c);// 1 2 5

// Accept variable number of arguments
int Sum(paramsint[] nums) {
int sum = 0;
foreach (int i in nums)
sum += i;
return sum;
}

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

/* C# doesn't support optional arguments/parameters. Just create two different versions of the same function. */
void SayHello(string name,string prefix) {
Console.WriteLine("Greetings," + prefix + " " + name);
}

void SayHello(string name) {
SayHello(name,"");
}

Special character constants
vbCrLf,vbCr,vbLf,vbNewLine
vbNullString
vbTab
vbBack
vbFormFeed
vbVerticalTab
""

' String concatenation (use & or +)
Dim school As String = "Harding"&vbTab
school = school & "University"' school is "Harding (tab) University"

' Chars
Dim letter AsChar= school.Chars(0)' letter is H
letter = Convert.ToChar(65)' letter is A
letter =Chr(65)' same thing
Dim word() As Char = school.ToCharArray()' word holds Harding

' No string literal operator
Dim msg As String = "File is c:"temp"x.dat"

' String comparison
Dim mascot As String = "Bisons"
If (mascot = "Bisons") Then' true
If (mascot.Equals("Bisons")) Then' true
If (mascot.ToUpper().Equals("BISONS")) Then' true
If (mascot.CompareTo("Bisons") = 0) Then' true

Console.WriteLine(mascot.Substring(2,3))' Prints "son"

' String matching
If ("John 3:16"Like"Jo[Hh]? #:*") Then'true

Imports System.Text.RegularExpressions' More powerful than Like
Dim r As NewRegex("Jo[hH]. "d:*")
If (r.Match("John 3:16").Success) Then'true

' My birthday: Oct 12,1973
Dim dt As New DateTime(1973,10,12)
Dim s As String = "My birthday: " & dt.ToString("MMM dd,yyyy")

' Mutable string
Dim buffer As New System.Text.StringBuilder("two ")
buffer.Append("three ")
buffer.Insert(0,"one ")
buffer.Replace("two","TWO")
Console.WriteLine(buffer)' Prints "one TWO three"

Escape sequences
"n,"r
"t
""
""

// String concatenation
stringschool = "Harding"t";
school = school + "University";// school is "Harding (tab) University"

// Chars
charletter = school[0];// letter is H
letter = Convert.ToChar(65);// letter is A
letter =(char)65;// same thing
char[]word = school.ToCharArray();// word holds Harding

// String literal
string msg =@"File is c:"temp"x.dat";
// same as
string msg = "File is c:""temp""x.dat";

// String comparison
string mascot = "Bisons";
if (mascot == "Bisons")// true
if (mascot.Equals("Bisons"))// true
if (mascot.ToUpper().Equals("BISONS"))// true
if (mascot.CompareTo("Bisons") == 0)// true

Console.WriteLine(mascot.Substring(2,3));// Prints "son"

// String matching
// No Like equivalent - use regular expressions

using System.Text.RegularExpressions;
Regexr = newRegex(@"Jo[hH]. "d:*");
if (r.Match("John 3:16").Success)// true

// My birthday: Oct 12,1973
DateTime dt = new DateTime(1973,12);
string s = "My birthday: " + dt.ToString("MMM dd,yyyy");

// Mutable string
System.Text.StringBuilderbuffer = new System.Text.StringBuilder("two ");
buffer.Append("three ");
buffer.Insert(0,"one ");
buffer.Replace("two","TWO");
Console.WriteLine(buffer);// Prints "one TWO three"

' Throw an exception
Dim ex As New Exception("Something is really wrong.")
Throw ex

' Catch an exception
Try
y = 0
x = 10 / y
Catchex As ExceptionWheny = 0' Argument and When is optional
Console.WriteLine(ex.Message)
Finally
Beep()
End Try

' Deprecated unstructured error handling
OnErrorGoToMyErrorHandler
...
MyErrorHandler: Console.WriteLine(Err.Description)

// Throw an exception
Exception up = new Exception("Something is really wrong.");
throwup;// ha ha

// Catch an exception
try{
y = 0;
x = 10 / y;
}
catch(Exception ex) {// Argument is optional,no "When" keyword
Console.WriteLine(ex.Message);
}
finally{
// Requires reference to the Microsoft.VisualBasic.dll
// assembly (pre .NET Framework v2.0)
Microsoft.VisualBasic.Interaction.Beep();
}

NamespaceHarding.Compsci.Graphics
...
End Namespace

' or

NamespaceHarding
NamespaceCompsci
NamespaceGraphics
...
End Namespace
End Namespace
End Namespace

ImportsHarding.Compsci.Graphics

namespaceHarding.Compsci.Graphics {
...
}

// or

namespaceHarding {
namespaceCompsci {
namespaceGraphics {
...
}
}
}

usingHarding.Compsci.Graphics;

Accessibility keywords
Public
Private
Friend
Protected
Protected Friend
Shared

' Inheritance
ClassFootballGame
InheritsCompetition
...
End Class

' Interface definition
InterfaceIAlarmClock
...
End Interface

// Extending an interface
InterfaceIAlarmClock
InheritsIClock
...
End Interface

// Interface implementation
ClassWristWatch
ImplementsIAlarmClock,ITimer
...
End Class

Accessibility keywords
public
private
internal
protected
protected internal
static

// Inheritance
classFootballGame:Competition {
...
}

// Interface definition
interfaceIAlarmClock {
...
}

// Extending an interface
interfaceIAlarmClock:IClock {
...
}

// Interface implementation
classWristWatch:IAlarmClock,ITimer {
...
}

ClassSuperHero
Private _powerLevel As Integer

Public SubNew()
_powerLevel = 0
End Sub

Public SubNew(ByVal powerLevel As Integer)
Me._powerLevel = powerLevel
End Sub

Protected Overrides SubFinalize()
' Desctructor code to free unmanaged resources
MyBase.Finalize()
End Sub
End Class

classSuperHero {
private int _powerLevel;

public SuperHero() {
_powerLevel = 0;
}

public SuperHero(int powerLevel) {
this._powerLevel= powerLevel;
}

~SuperHero() {
// Destructor code to free unmanaged resources.
// Implicitly creates a Finalize method
}
}

Dim hero As SuperHero = New SuperHero
' or
Dim hero As New SuperHero

Withhero
.Name = "SpamMan"
.PowerLevel = 3
End With

hero.Defend("Laura Jones")
hero.Rest()' Calling Shared method
' or
SuperHero.Rest()

Dim hero2 As SuperHero = hero' Both reference the same object
hero2.Name = "WormWoman"
Console.WriteLine(hero.Name)' Prints WormWoman

hero =Nothing' Free the object

If heroIsNothingThen _
hero = New SuperHero

Dim obj As Object = New SuperHero
IfTypeOfobjIsSuperHero Then _
Console.WriteLine("Is a SuperHero object.")

' Mark object for quick disposal
Usingreader As StreamReader = File.OpenText("test.txt")
Dim line As String = reader.ReadLine()
While Not line Is Nothing
Console.WriteLine(line)
line = reader.ReadLine()
End While
End Using

SuperHero hero = new SuperHero();

// No "With" construct
hero.Name = "SpamMan";
hero.PowerLevel = 3;

hero.Defend("Laura Jones");
SuperHero.Rest();// Calling static method

SuperHero hero2 = hero;// Both reference the same object
hero2.Name = "WormWoman";
Console.WriteLine(hero.Name);// Prints WormWoman

hero =null;// Free the object

if (hero ==null)
hero = new SuperHero();

Object obj = new SuperHero();
if (objisSuperHero)
Console.WriteLine("Is a SuperHero object.");

// Mark object for quick disposal
using(StreamReader reader = File.OpenText("test.txt")) {
string line;
while ((line = reader.ReadLine()) != null)
Console.WriteLine(line);
}

StructureStudentRecord
Public name As String
Public gpa As Single

Public Sub New(ByVal name As String,ByVal gpa As Single)
Me.name = name
Me.gpa = gpa
End Sub
End Structure

Dim stu As StudentRecord = New StudentRecord("Bob",3.5)
Dim stu2 As StudentRecord = stu

stu2.name = "Sue"
Console.WriteLine(stu.name)' Prints Bob
Console.WriteLine(stu2.name)' Prints Sue

structStudentRecord {
public string name;
public float gpa;

public StudentRecord(string name,float gpa) {
this.name = name;
this.gpa = gpa;
}
}

StudentRecord stu = new StudentRecord("Bob",3.5f);
StudentRecord stu2 = stu;

stu2.name = "Sue";
Console.WriteLine(stu.name);// Prints Bob
Console.WriteLine(stu2.name);// Prints Sue

Private _size As Integer

PublicPropertySize() 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++;

DelegateSub MsgArrivedEventHandler(ByVal message As String)

EventMsgArrivedEvent As MsgArrivedEventHandler

' or to define an event which declares a delegate implicitly
EventMsgArrivedEvent(ByVal message As String)

AddHandlerMsgArrivedEvent,AddressOfMy_MsgArrivedCallback
' Won't throw an exception if obj is Nothing
RaiseEventMsgArrivedEvent("Test message")
RemoveHandlerMsgArrivedEvent,AddressOfMy_MsgArrivedCallback

Imports System.Windows.Forms

DimWithEventsMyButton As Button' WithEvents can't be used on local variable
MyButton = New Button

Private Sub MyButton_Click(ByVal sender As System.Object,_
ByVal e As System.EventArgs)HandlesMyButton.Click
MessageBox.Show(Me,"Button was clicked","Info",_
MessageBoxButtons.OK,MessageBoxIcon.Information)
End Sub

delegatevoid MsgArrivedEventHandler(string message);

eventMsgArrivedEventHandler MsgArrivedEvent;

// Delegates must be used with events in C#


MsgArrivedEvent+=new MsgArrivedEventHandler(My_MsgArrivedEventCallback);
MsgArrivedEvent("Test message");// Throws exception if obj is null
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,
MessageBoxButtons.OK,MessageBoxIcon.Information);
}

Console.Write("What's your name? ")
Dim name As String = Console.ReadLine()
Console.Write("How old are you? ")
Dim age As Integer = Val(Console.ReadLine())
Console.WriteLine("{0} is {1} years old.",name,age)
' or
Console.WriteLine(name & " is " & age & " years old.")

Dim c As Integer
c = Console.Read()' Read single char
Console.WriteLine(c)' Prints 65 if user enters "A"

Console.Write("What's your name? ");
string name = Console.ReadLine();
Console.Write("How old are you? ");
int age = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("{0} is {1} years old.",age);
// or
Console.WriteLine(name + " is " + age + " years old.");

int c = Console.Read();// Read single char
Console.WriteLine(c);// Prints 65 if user enters "A"

Imports System.IO

' Write out to text file
Dim writer AsStreamWriter= File.CreateText("c:"myfile.txt")
writer.WriteLine("Out to file.")
writer.Close()

' Read all lines from text file
Dim reader AsStreamReader= 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 NewBinaryWriter(File.OpenWrite("c:"myfile.dat"))
binWriter.Write(str)
binWriter.Write(num)
binWriter.Close()

' Read from binary file
Dim binReader As NewBinaryReader(File.OpenRead("c:"myfile.dat"))
str = binReader.ReadString()
num = binReader.ReadInt32()
binReader.Close()

using System.IO;

// Write out to text file
StreamWriterwriter = File.CreateText("c:""myfile.txt");
writer.WriteLine("Out to file.");
writer.Close();

// Read all lines from text file
StreamReaderreader = 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;
BinaryWriterbinWriter = new BinaryWriter(File.OpenWrite("c:""myfile.dat"));
binWriter.Write(str);
binWriter.Write(num);
binWriter.Close();

// Read from binary file
BinaryReaderbinReader = new BinaryReader(File.OpenRead("c:""myfile.dat")); str = binReader.ReadString(); num = binReader.ReadInt32(); binReader.Close();