VB.NET and C# Comparison

VB.NET and C# Comparison
This is a quick reference guide to highlight some key syntactical differences between VB.NET and C#. Hope you find this useful!
Thank you to Tom Shelton, Fergus Cooney, Steven Swafford, Gjuro Kladaric, and others for your contributions.





VB.NET Program Structure C#
Imports System

Namespace Hello
   Class HelloWorld
      Overloads Shared Sub Main(ByVal args() As String)
         Dim name As String = "VB.NET"

         'See if an argument was passed from the command line
          If args.Length = 1 Then name = args(0)

          Console.WriteLine("Hello, " & name & "!")
      End Sub
   End Class
End Namespace 		using System;

namespace Hello {
   public class HelloWorld {
      public static void Main(string[] args) {
         string name = "C#";

         // See if an argument was passed from the command line
         if (args.Length == 1)
            name = args[0];

         Console.WriteLine("Hello, " + name + "!");
      }
   }
}
VB.NET Comments C#
' 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> */

VB.NET Data Types C#

Value Types
Boolean
Byte, SByte
Char
Short, UShort, Integer, UInteger, Long, ULong
Single, Double
Decimal
Date   (alias of System.DateTime)

Reference Types
Object
String

Initializing
Dim correct As Boolean = True
Dim b As Byte = &H2A   'hex or &O52 for octal
Dim person As Object = Nothing
Dim name As String = "Dwight"
Dim grade As Char = "B"c
Dim today As Date = #12/31/2010 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

Implicitly Typed Local Variables
Dim s = "Hello!"
Dim nums = New Integer() {1, 2, 3}
Dim hero = New SuperHero With {.Name = "Batman"}

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

Dim c as New Circle
If TypeOf c Is Shape Then _
    Console.WriteLine("c is a Shape")

Type Conversion / Casting
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)

Dim o As Object = 2
i = DirectCast(o, Integer)   ' Throws InvalidCastException if type cast fails

Dim s As New Shape
Dim c As Circle = TryCast(s, Circle)   ' Returns Nothing if type cast fails

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("12/31/2010 12:15:00 PM");
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;

Implicitly Typed Local Variables
var s = "Hello!";
var nums = new int[] { 1, 2, 3 };
var hero = new SuperHero() { Name = "Batman" };

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

Circle c = new Circle();
if (c is Shape)
    Console.WriteLine("c is a Shape");

Type Conversion / Casting
float d = 3.5f;
i = Convert.ToInt32(d);     // Set to 4 (rounds)
int i = (int)d;     // set to 3 (truncates decimal)


object o = 2;
int i = (int)o;   // Throws InvalidCastException if type cast fails

Shape s = new Shape();
Circle c = s as Circle;   // Returns null if type cast fails

VB.NET Constants C#
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;

VB.NET Enumerations C#
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
VB.NET Operators C#

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
+

VB.NET Choices C#

' Ternary/Conditional operator (IIf evaluates 2nd and 3rd expressions)
greeting = If(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?" Else greeting = "Hello"

' Use : to put two commands on same line
If x <> 100 AndAlso y < 5 Then x *= 5 : y *= 2  

' Preferred
If x <> 100 AndAlso y < 5 Then
  x *= 5
  y *= 2
End If

' Use _ to break up long single line or use implicit line break
If whenYouHaveAReally < longLine And
  itNeedsToBeBrokenInto2 > Lines Then _
  UseTheUnderscore(charToBreakItUp)

'If x > 5 Then
  x *= y
ElseIf x = 5 OrElse y Mod 2 = 0 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

// Ternary/Conditional operator
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 || y % 2 == 0)
  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
}

VB.NET Loops C#
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 Step 2
  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 <= 4; i++) {
  if (i < 4)
    continue;
  Console.WriteLine(i);   // Only prints 4
}

VB.NET Arrays C#

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

// Add two elements, keeping the existing values
Array.Resize(ref names, 7);

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;

VB.NET Functions C#

' 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 As Integer()) 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("Mom")

 // 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# 4.0 supports optional parameters. Previous versions required function overloading. */ 
void SayHello(string name, string prefix = "") {
  Console.WriteLine("Greetings, " + prefix + " " + name);
} 

SayHello("Strangelove", "Dr.");
SayHello("Mom");

VB.NET Strings C#

Special character constants (all also accessible from ControlChars class)
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 = "Z"c                                         ' letter is Z
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

' String matching with Like - Regex is more powerful
If ("John 3:16" Like "Jo[Hh]? #:*") Then   'true

' Substring
s = mascot.Substring(2, 3)) ' s is "son"

' Replacement
s = mascot.Replace("sons", "nomial")) ' s is "Binomial"

' Split
Dim names As String = "Michael,Dwight,Jim,Pam"
Dim parts() As String = names.Split(",".ToCharArray())   ' One name in each slot

' Date to string
Dim dt As New DateTime(1973, 10, 12)
Dim s As String = "My birthday: " & dt.ToString("MMM dd, yyyy")   ' Oct 12, 1973

' Integer to String
Dim x As Integer = 2
Dim y As String = x.ToString()     ' y is "2"

' String to Integer
Dim x As Integer = Convert.ToInt32("-5")     ' x is -5

' 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 = 'Z';                               // letter is Z
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

// String matching - No Like equivalent, use Regex


// Substring
s = mascot.Substring(2, 3))     // s is "son"

// Replacement
s = mascot.Replace("sons", "nomial"))     // s is "Binomial"

// Split
string names = "Michael,Dwight,Jim,Pam";
string[] parts = names.Split(",".ToCharArray());   // One name in each slot

// Date to string
DateTime dt = new DateTime(1973, 10, 12);
string s = dt.ToString("MMM dd, yyyy");     // Oct 12, 1973

// int to string
int x = 2;
string y = x.ToString();     // y is "2"

// string to int
int x = Convert.ToInt32("-5");     // x is -5

 

// 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"

VB.NET Regular Expressions C#

Imports System.Text.RegularExpressions

' Match a string pattern
Dim r As New Regex("j[aeiou]h?. \d:*", RegexOptions.IgnoreCase Or _
        RegexOptions.Compiled)
If (r.Match("John 3:16").Success) Then   'true
    Console.WriteLine("Match")
End If

' Find and remember all matching patterns
Dim s As String = "My number is 305-1881, not 305-1818."
Dim r As New Regex("(\d+-\d+)")
Dim m As Match = r.Match(s)     ' Matches 305-1881 and 305-1818
While m.Success
    Console.WriteLine("Found number: " & m.Groups(1).Value & " at position " _
            & m.Groups(1).Index.ToString)
    m = m.NextMatch()
End While

' Remeber multiple parts of matched pattern
Dim r As New Regex("(\d\d):(\d\d) (am|pm)")
Dim m As Match = r.Match("We left at 03:15 pm.")
If m.Success Then
    Console.WriteLine("Hour: " & m.Groups(1).ToString)       ' 03
    Console.WriteLine("Min: " & m.Groups(2).ToString)         ' 15
    Console.WriteLine("Ending: " & m.Groups(3).ToString)   ' pm
End If

' Replace all occurrances of a pattern
Dim r As New Regex("h\w+?d", RegexOptions.IgnoreCase)
Dim s As String = r.Replace("I heard this was HARD!", "easy")   ' I easy this was easy!

' Replace matched patterns
Dim s As String = Regex.Replace("123 < 456", "(\d+) . (\d+)", "$2 > $1")   ' 456 > 123

' Split a string based on a pattern
Dim names As String = "Michael, Dwight, Jim, Pam"
Dim r As New Regex(",\s*")
Dim parts() As String = r.Split(names)   ' One name in each slot

using System.Text.RegularExpressions;

// Match a string pattern
Regex r = new Regex(@"j[aeiou]h?. \d:*", RegexOptions.IgnoreCase |
        RegexOptions.Compiled);
if (r.Match("John 3:16").Success)   // true
    Console.WriteLine("Match");


// Find and remember all matching patterns
string s = "My number is 305-1881, not 305-1818.";
Regex r = new Regex("(\\d+-\\d+)");
// Matches 305-1881 and 305-1818
for (Match m = r.Match(s); m.Success; m = m.NextMatch())
    Console.WriteLine("Found number: " + m.Groups[1] + " at position " +
        m.Groups[1].Index);



// Remeber multiple parts of matched pattern
Regex r = new Regex("@(\d\d):(\d\d) (am|pm)");
Match m = r.Match("We left at 03:15 pm.");
if (m.Success) {
    Console.WriteLine("Hour: " + m.Groups[1]);       // 03
    Console.WriteLine("Min: " + m.Groups[2]);         // 15
    Console.WriteLine("Ending: " + m.Groups[3]);   // pm
}

// Replace all occurrances of a pattern
Regex r = new Regex("h\\w+?d", RegexOptions.IgnoreCase);
string s = r.Replace("I heard this was HARD!", "easy"));   // I easy this was easy!

// Replace matched patterns
string s = Regex.Replace("123 < 456", @"(\d+) . (\d+)", "$2 > $1");   // 456 > 123

// Split a string based on a pattern
string names = "Michael, Dwight, Jim, Pam";
Regex r = new Regex(@",\s*");
string[] parts = r.Split(names);   // One name in each slot

VB.NET Exception Handling C#

' 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 {
  Microsoft.VisualBasic.Interaction.Beep();
}

VB.NET Namespaces C#

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;

VB.NET Classes / Interfaces C#

Access Modifiers
Public
Private
Friend
Protected
Protected Friend

Class Modifiers
MustInherit
NotInheritable

Method Modifiers
MustOverride
NotInheritable
Shared
Overridable

' All members are Shared
Module

' Partial classes
Partial Class Competition
  ...
End Class 

' Inheritance
Class FootballGame
  Inherits Competition
  ...
End Class 

' Interface definition
Interface IAlarmClock
  Sub Ring()
  Property TriggerDateTime() As DateTime
End Interface

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

' Interface implementation
Class WristWatch 
  Implements IAlarmClock, ITimer

  Public Sub Ring() Implements IAlarmClock.Ring
    Console.WriteLine("Wake up!")
  End Sub

  Public Property TriggerDateTime As DateTime Implements IAlarmClock.TriggerDateTime
  ...
End Class 

Access Modifiers
public
private
internal
protected
protected internal

Class Modifiers
abstract
sealed
static

Method Modifiers
abstract
sealed
static
virtual

No Module equivalent - just use static class

// Partial classes
partial class Competition {
  ...
}

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


// Interface definition
interface IAlarmClock {
  void Ring();
  DateTime CurrentDateTime { get; set; }
}

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


// Interface implementation
class WristWatch : IAlarmClock, ITimer {

  public void Ring() {
    Console.WriteLine("Wake up!");
  }

  public DateTime TriggerDateTime { get; set; }
  ...
}

VB.NET Constructors / Destructors C#
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

  Shared Sub New()
    ' Shared constructor invoked before 1st instance is created
  End Sub

  Protected Overrides Sub Finalize() 
   ' Destructor 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; 
  }

  static SuperHero() {
    // Static constructor invoked before 1st instance is created
  }

  ~SuperHero() {
    // Destructor implicitly creates a Finalize method
  }
}

VB.NET Using Objects C#

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 Is Nothing 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" but can use object initializers
SuperHero hero = new SuperHero() { Name = "SpamMan", 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);
}
VB.NET Structs C#

Structure Student
  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 Student = New Student("Bob", 3.5)
Dim stu2 As Student = stu  

stu2.name = "Sue"
Console.WriteLine(stu.name)    ' Prints Bob
Console.WriteLine(stu2.name)  ' Prints Sue

 struct Student {
  public string name;
  public float gpa;

  public Student(string name, float gpa) {
    this.name = name;
    this.gpa = gpa;
  }
}

Student stu = new Student("Bob", 3.5f);
Student stu2 = stu;  

stu2.name = "Sue";
Console.WriteLine(stu.name);    // Prints Bob
Console.WriteLine(stu2.name);   // Prints Sue

VB.NET Properties C#

' Auto-implemented properties are new to VB10
Public Property Name As String
Public Property Size As Integer = -1     ' Default value, Get and Set both Public

' Traditional property implementation
Private mName As String
Public Property Name() As String
    Get
        Return mName
    End Get
    Set(ByVal value As String)
        mName = value
    End Set
End Property

' Read-only property
Private mPowerLevel As Integer
Public ReadOnly Property PowerLevel() As Integer
    Get
        Return mPowerLevel
    End Get
End Property

' Write-only property
Private mHeight As Double
Public WriteOnly Property Height() As Double
    Set(ByVal value As Double)
        mHeight = If(value < 0, mHeight = 0, mHeight = value)
    End Set
End Property

// Auto-implemented properties
public string Name { get; set; }
public int Size { get; protected set; }     // Set default value in constructor

// Traditional property implementation
private string name;
public string Name {
  get {
    return name;
  }
  set {
    name = value;
  }
}

// Read-only property
private int powerLevel;
public int PowerLevel {
  get {
    return powerLevel;
  }
}

// Write-only property
private double height;
public double Height {
  set {
    height = value < 0 ? 0 : value;
  }
}

VB.NET Delegates / Events C#

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

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) 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);
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);
}

VB.NET Generics C#

' Enforce accepted data type at compile-time
Dim numbers As New List(Of Integer)
numbers.Add(2)
numbers.Add(4)
DisplayList(Of Integer)(numbers)

' Subroutine can display any type of List
Sub DisplayList(Of T)(ByVal list As List(Of T))
    For Each item As T In list
        Console.WriteLine(item)
    Next
End Sub

' Class works on any data type
Class SillyList(Of T)
    Private list(10) As T
    Private rand As New Random

    Public Sub Add(ByVal item As T)
        list(rand.Next(10)) = item
    End Sub

    Public Function GetItem() As T
        Return list(rand.Next(10))
    End Function
End Class

' Limit T to only types that implement IComparable
Function Maximum(Of T As IComparable)(ByVal ParamArray items As T()) As T
    Dim max As T = items(0)
    For Each item As T In items
        If item.CompareTo(max) > 0 Then max = item
    Next
    Return max
End Function

// Enforce accepted data type at compile-time
List<int> numbers = new List<int>();
numbers.Add(2);
numbers.Add(4);
DisplayList<int>(numbers);

// Function can display any type of List
void DisplayList<T>(List<T> list) {
    foreach (T item in list)
        Console.WriteLine(item);
}

// Class works on any data type
class SillyList<T> {
    private T[] list = new T[10];
    private Random rand = new Random();

    public void Add(T item) {
        list[rand.Next(10)] = item;
    }

    public T GetItem() {
        return list[rand.Next(10)];
    }
}

// Limit T to only types that implement IComparable
T Maximum<T>(params T[] items) where T : IComparable<T> {
    T max = items[0];
    foreach (T item in items)
        if (item.CompareTo(max) > 0)
            max = item;
    return max;
}

VB.NET LINQ C#

Dim nums() As Integer = {5, 8, 2, 1, 6}

' Get all numbers in the array above 4
Dim results = From value In nums
                  Where value > 4
                  Select value

Console.WriteLine(results.Count())     ' 3
Console.WriteLine(results.First())     ' 5
Console.WriteLine(results.Last())     ' 6
Console.WriteLine(results.Average())     ' 6.33333

' Displays 5 8 6
For Each n As Integer In results
    Console.Write(n & " ")
Next

results = results.Intersect({5, 6, 7})     ' 5 6
results = results.Concat({5, 1, 5})     ' 5 6 5 1 5
results = results.Distinct()     ' 5 6 1

Dim Students() As Student = {
    New Student With {.Name = "Bob", .GPA = 3.5},
    New Student With {.Name = "Sue", .GPA = 4.0},
    New Student With {.Name = "Joe", .GPA = 1.9}
}

' Get an ordered list of all students by GPA with GPA >= 3.0
Dim goodStudents = From s In Students
            Where s.GPA >= 3.0
            Order By s.GPA Descending
            Select s

Console.WriteLine(goodStudents.First.Name)     ' Sue

 int[] nums = { 5, 8, 2, 1, 6 };

// Get all numbers in the array above 4
var results = from value in nums
                where value > 4
                select value;

Console.WriteLine(results.Count());     // 3
Console.WriteLine(results.First());     // 5
Console.WriteLine(results.Last());     // 6
Console.WriteLine(results.Average());     // 6.33333

// Displays 5 8 6
foreach (int n in results)
    Console.Write(n + " ");


results = results.Intersect(new[] {5, 6, 7});     // 5 6
results = results.Concat(new[] {5, 1, 5});     // 5 6 5 1 5
results = results.Distinct();     // 5 6 1

Student[] Students = {
    new Student{ Name = "Bob", GPA = 3.5 },
    new Student{ Name = "Sue", GPA = 4.0 },
    new Student{ Name = "Joe", GPA = 1.9 }
};

// Get an ordered list of all students by GPA with GPA >= 3.0
var goodStudents = from s in Students
            where s.GPA >= 3.0
            orderby s.GPA descending
            select s;

Console.WriteLine(goodStudents.First().Name);     // Sue
VB.NET Console I/O C#

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"

VB.NET File I/O C#

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();

posted @ 2011-10-19 09:04  中尉  阅读(429)  评论(0)  编辑  收藏  举报