VB C# 语法对比图 ，代码实例

Comments

VB.NET

'Single line only
Rem Single line only

C#

// 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)

C#

//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

C#

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())

C#

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
& 

C#

//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

C#

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)
Next 



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

C#

//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);

Arrays

VB.NET

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

C#

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
  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")

C#

// 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

C#

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
  End Namespace
End Namespace 


Imports ASPAlliance.DotNet.Community

C#

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

C#

//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

C#

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.")

C#

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

C#

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

C#

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

C#

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"

C#

//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"

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()

C#

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();