VB.NET and C# 的语法区别举例

// Single line
/* Multiple
line */
/// <summary>XML comments on single line</summary>
/** <summary>XML comments on multiple lines</summary> */

Value Types
Boolean
Byte,SByte
Char
Short,UShort,Integer,UInteger,Long,ulong
Single,Double
Decimal
Date

Reference Types
Object
String

Initializing
Dim correct As Boolean = True
Dim b As Byte = &H2A 'hex
Dim o As Byte = &O52 'octal
Dim person As Object = nothing
Dim name As String = "DWight"
Dim grade As Char = "B"c
Dim today As Date = #12/31/2007 12:15:00 PM#
Dim amount As Decimal = 35.99@
Dim gpa As Single = 2.9!
Dim pi As Double = 3.14159265
Dim lTotal As Long = 123456L
Dim sTotal As Short = 123S
Dim usTotal As UShort = 123US
Dim uiTotal As UInteger = 123UI
Dim ulTotal As ulong = 123ul

Type information
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
short,ushort,int,uint,long,ulong
float,double
decimal
DateTime(not a built-in C#type)

Reference Types
object
string

Initializing
bool correct = true;
byte b = 0x2A; // hex

object person = null;
string name = "DWight";
char grade = 'B';
DateTime today = DateTime.Parse("12/31/2007 12:15:00");
decimal amount = 35.99m;
float gpa = 2.9f;
double pi = 3.14159265;
long lTotal = 123456L;
short sTotal = 123;
ushort usTotal = 123;
uint uiTotal = 123;
ulong ulTotal = 123;

Type information
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 to3 (truncates decimal)

' Can set to a const orvar; may be initialized in a constructor
ReadonlyMIN_DIAMETERAsSingle = 4.93

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

Comparison
= < > <= >= <>

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

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

Bitwise
And Or Xor 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

// 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
}

' Pass by value (in,default),reference (in/out),andreference (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 ' cset to zero by default
TestFunc(a,b,c)
Console.Writeline("{0} {1} {2}",a,c)' 12 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 beListed lastand 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")

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'tsupport 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
/r // carriage-return
/n // line-Feed
/t // tab
// // backslash
/" // quote

// 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
stringmascot = "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.")
Throwex

' 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 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.");

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

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

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();