VB.NET	C#.NET
' Single line only *REM* Single line only ''' <summary>XML comments</summary>	// Single line /* Multiple line / /// <summary>XML comments on single line</summary> /* <summary>XML comments on multiple lines</summary> */

2.3 Data Types

VB.NET

C#.NET

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
Dim x As Integer
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 to 3 (truncates decimal)

2.4 Constants

VB.NET

C#.NET

Const MAX_STUDENTS As Integer = 25

' Can set to a const or var; may be initialized in a constructor
ReadOnly MIN_DIAMETER As Single = 4.93

const int MAX_STUDENTS = 25;

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

2.5 Enumerations

VB.NET

C#.NET

Enum Action
Start
[Stop] ' Stop is a reserved word
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 _
Console.WriteLine(a.ToString & " is " & a) ' Prints "Stop is 1"

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

enum Action {Start, Stop, Rewind, Forward};
enum Status {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

2.6 Operators

VB.NET

C#.NET

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
+

2.7 Choices

VB.NET

C#.NET

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

' One line doesn't require "End If"
If age < 20 Then greeting = "What's up?"
If age < 20 Then greeting = "What's up?" Elsegreeting = "Hello"

' 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

' To break up any long single line use _
If whenYouHaveAReally < 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

Select Case color   ' 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;
else if (x == 5)
x += y;
else if (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
}

2.8 Loops

VB.NET

C#.NET

Pre-test Loops:

While c < 10 c += 1 End While	Do Until c = 10 c += 1 Loop
Do While c < 10 c += 1 Loop	For c = 2 To 10 Step2 Console.WriteLine(c) Next

Post-test Loops:

Do
c += 1
Loop While c < 10

Do
c += 1
Loop Until c = 10

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

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

' Continue to next iteration
For i = 0 To 4
If i < 4 Then Continue 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", "Sue", "Barney"};
foreach (string s in names)
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
}

2.9 Arrays

VB.NET

C#.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) = "David"
names(5) = "Bobby" ' Throws System.IndexOutOfRangeException

' 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] = "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;

2.10 Functions

VB.NET

C#.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

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

' Accept variable number of arguments
Function Sum(ByVal ParamArray nums AsInteger()) 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, 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 = "")
Console.WriteLine("Greetings, " & prefix & " " & name)
End Sub

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

// 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);
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) {
Console.WriteLine("Greetings, " + prefix + " " + name);
}

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

2.11 Strings

VB.NET

C#.NET

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 As Char = 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 New Regex("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
string school = "Harding"t";
school = school + "University"; // school is "Harding (tab) University"

// Chars
char letter = 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;
Regex r = new Regex(@"Jo[hH]. "d:*");
if (r.Match("John 3:16").Success) // true

// My birthday: Oct 12, 1973
DateTime dt = new DateTime(1973, 10, 12);
string s = "My birthday: " + dt.ToString("MMM dd, yyyy");

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

2.12 Exception Handling

VB.NET

C#.NET

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

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

' Deprecated unstructured error handling
On Error GoTo MyErrorHandler
...
MyErrorHandler: Console.WriteLine(Err.Description)

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

2.13 Namespaces

VB.NET

C#.NET

Namespace Harding.Compsci.Graphics
...
End Namespace

' or

Namespace Harding
  Namespace Compsci
    Namespace Graphics
      ...
    End Namespace
  End Namespace
End Namespace

Imports Harding.Compsci.Graphics

namespace Harding.Compsci.Graphics {
...
}

// or

namespace Harding {
  namespace Compsci {
    namespace Graphics {
      ...
    }
}
}

using Harding.Compsci.Graphics;

2.14 Classes / Interfaces

VB.NET

C#.NET

Accessibility keywords
Public
Private
Friend
Protected
Protected Friend
Shared

' Inheritance
Class FootballGame
Inherits Competition
...
End Class

' Interface definition
Interface IAlarmClock
...
End Interface

// Extending an interface
Interface IAlarmClock
Inherits IClock
...
End Interface

// Interface implementation
Class WristWatch
Implements IAlarmClock, ITimer
...
End Class

Accessibility keywords
public
private
internal
protected
protected internal
static

// Inheritance
class FootballGame : Competition {
...
}

// Interface definition
interface IAlarmClock {
...
}

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

// Interface implementation
class WristWatch : IAlarmClock, ITimer {
...
}

2.15 Constructors / Destructors

VB.NET

C#.NET

Class SuperHero
Private _powerLevel As Integer

Public Sub New()
_powerLevel = 0
End Sub

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

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

class SuperHero {
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
}
}

2.16 Using Objects

VB.NET

C#.NET

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

With hero
.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 hero IsNothing Then _
hero = New SuperHero

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

' Mark object for quick disposal
Using reader 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 (obj is SuperHero)
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);
}

2.17 Structs

VB.NET

C#.NET

Structure StudentRecord
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

struct StudentRecord {
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

2.18 Properties

VB.NET

C#.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

private int _size;

public int Size {
  get {
    return _size;
}
  set {
if (value < 0)
_size = 0;
else
_size = value;
}
}

foo.Size++;

2.19 Delegates / Events

VB.NET

C#.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, AddressOfMy_MsgArrivedCallback
' Won't throw an exception if obj is Nothing
RaiseEvent MsgArrivedEvent("Test message")
RemoveHandler MsgArrivedEvent, AddressOfMy_MsgArrivedCallback

Imports System.Windows.Forms

Dim WithEvents MyButton 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

delegate void MsgArrivedEventHandler(string message);

event MsgArrivedEventHandler 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, "Button was clicked", "Info",
MessageBoxButtons.OK, MessageBoxIcon.Information);
}

2.20 Console I/O

VB.NET

C#.NET

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.", name, 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"

2.21 File I/O

VB.NET

C#.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 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
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();

秒客网

C# 与 VB.NET 对比

C# 与 VB.NET 对比

1.0 Introduction

1.1 Purpose & Scope

2.0 Comparison

2.1 Program Structure

2.2 Comments

2.3 Data Types

2.4 Constants

2.5 Enumerations

2.6 Operators

2.7 Choices

2.8 Loops

2.9 Arrays

2.10 Functions

2.11 Strings

2.12 Exception Handling

2.13 Namespaces

2.14 Classes / Interfaces

2.15 Constructors / Destructors

2.16 Using Objects

2.17 Structs

2.18 Properties

2.19 Delegates / Events

2.20 Console I/O

2.21 File I/O

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