VB C# 语法对比图 (代码实例)

VB C# 语法对比图 (代码实例)

C#和VB.net的语法相差还是比较大的. 可能你会C#,可能你会VB.

将它们俩放在一起对比一下你就会很快读懂,并掌握另一门语言.

相信下面这张图会对你帮助很大.

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();