C#和VB.net语法对比

'Single line only
Rem Single line only

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

'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

Const MAX_AUTHORS As Integer = 25
ReadOnly MIN_RANK As Single = 5.00

const int MAX_AUTHORS = 25;
readonly float MIN_RANKING = 5.00;

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);

'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
+

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;
}

'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)
Next
'Array or collection looping
Dim names As String() = {"Steven", "SuOk", "Sarah"}
For Each s As String In names
　System.Console.WriteLine(s)
Next

//Pre-test Loops: while (i < 10)
　i++;
for (i = 2; i < = 10; i += 2)
　System.Console.WriteLine(i);
//Post-test Loop:
do
　i++;
while (i < 10);
// Array or collection looping
string[] names = {"Steven", "SuOk", "Sarah"};
foreach (string s in names)
　System.Console.WriteLine(s);

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) = "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;

'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
　Next
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'tsupport 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, "");
}

'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
}

Namespace ASPAlliance.DotNet.Community
　...
End Namespace
'or
Namespace ASPAlliance
　Namespace DotNet
　　Namespace Community
　　　...
　　End Namespace
　End Namespace
End Namespace
Imports ASPAlliance.DotNet.Community

namespace ASPAlliance.DotNet.Community {
　...
}
// or
namespace ASPAlliance {
　namespace DotNet {
　　namespace Community {
　　　...
　　}
　}
}
using ASPAlliance.DotNet.Community;

'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 {
　 ...
}

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
　}
}

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.");

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

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++;

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);
}

'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
t
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"

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();