VB.NET vs. C#

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

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 + "!");
      }
   }
}

Reference Types
Object
String
arrays
delegates

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 = [email protected]
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

Nullable Types
Dim x? As Integer = Nothing

Anonymous Types
Dim stu = New With {.Name = "Sue", .Gpa = 3.4}
Dim stu2 = New With {Key .Name = "Bob", .Gpa = 2.9}

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
isShape = TypeOf c Is Shape   ‘ True if c is a Shape

isSame = o1 Is o2   //
True if o1 and o2 reference same object

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 s As New Shape
Dim c As Circle = TryCast(s, Circle)   ‘ Returns Nothing if type cast fails
c = DirectCast(s, Circle)   ‘
Throws InvalidCastException if type cast fails

Reference Types
object
string
arrays
delegates

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;   // or
3.14159265D
long lTotal = 123456L;
short sTotal = 123;
ushort usTotal = 123;
uint uiTotal = 123;   // or 123U
ulong ulTotal = 123;   // or 123UL

Nullable Types
int? x = null;

Anonymous
Types
var stu = new {Name = "Sue", Gpa = 3.5};
var stu2 = new {Name = "Bob", Gpa = 2.9};   // no Key equivalent

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();
isShape = c is Shape;   // true if c is a Shape

isSame = Object.ReferenceEquals(o1, o2)   // true if o1 and o2 reference same object

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

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

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

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

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

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

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
&

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
+

‘ 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
}

‘  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

// 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
}

‘ 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

// 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;

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")

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");

‘ String concatenation (use & or
+) 
Dim school As String = "Harding" & vbTab
school = school & "University"   ‘ school is "Harding (tab) University"
school &= "University"   ‘ Same thing (+= does the same)

‘ 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 filename As String = "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"

// String concatenation
string school = "Harding\t";
school = school + "University";   // school is "Harding (tab) University" 
school += "University";   // Same thing

// 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 filename = @"c:\temp\x.dat";   // Same as "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"

‘ 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

// 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

‘ 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)

// 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(); 
}

‘ or

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

Imports Harding.Compsci.Graphics

// or

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

using Harding.Compsci.Graphics;

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

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; }
  ...
}

Private powerLevel As Integer
  Private name As String

‘ Default constructor
  Public Sub New() 
    powerLevel = 0
    name = "Super Bison" 
  End Sub

Public Sub New(ByVal powerLevel As Integer) 
    Me.New("Super Bison")   ‘ Call other constructor
    Me.powerLevel = powerLevel 
  End Sub

Public Sub New(ByVal name As String) 
    MyBase.New(name)   ‘ Call base classes‘ constructor 
    Me.name = name
  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

private int powerLevel;
  private string name;

// Default constructor
  public SuperHero() {
    powerLevel = 0;
    name = "Super Bison";
  }

public SuperHero(int powerLevel) 
    : this("Super Bison") {   // Call other constructor
    this.powerLevel = powerLevel; 
  }

public SuperHero(string name)
    : base(name) {   // Call base classes‘ constructor
    this.name = name;
  }

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

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

}

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

// 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);
}

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

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

‘ 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

// 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;
  }
}

‘ 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

// 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;
}

Sub SayHello(ByVal s As String)
  Console.WriteLine("Hello, " & s)
End Sub

‘ Create
delegate that calls SayHello
Dim hello As HelloDelegate = AddressOf SayHello
hello("World")   ‘ Or
hello.Invoke("World")

‘ Use lambda expression (anonymous
method) instead of a delegate
Dim hello2 = Sub(x) Console.WriteLine("Hello, " & x)
hello2("World")

‘ Use Func(Of T, TResult) delegate
to call Uppercase
Dim convert As Func(Of String, String) = AddressOf Uppercase
Console.WriteLine(convert("test"))

Function Uppercase(s As String) As String
  Return s.ToUpper()
End Function

‘ Declare and invoke lambda
expression
Console.WriteLine((Function(num As Integer) num + 1)(2))

‘ Pass lambda expression as an
argument
TestValues(Function(x, y) x Mod y = 0)

Sub TestValues(ByVal f As Func(Of
Integer, Integer, Boolean))
  If f(8, 4) Then
    Console.WriteLine("true")
  Else
    Console.WriteLine("false")
  End If
End Sub

void SayHello(string s) {
  Console.WriteLine("Hello, " + s);
}

// C# 1.0 delegate syntax with named
method
HelloDelegate hello = new HelloDelegate(SayHello);
hello("World");   // Or
hello.Invoke("World");

// C# 2.0 delegate syntax with
anonymous method
HelloDelegate hello2 = delegate(string s) { 
  Console.WriteLine("Hello, " + s); 
};
hello2("World");

// C# 3.0 delegate syntax with
lambda expression
HelloDelegate hello3 = s => {
Console.WriteLine("Hello, " + s); };
hello3("World");

// Use Func<in T, out TResult>
delegate to call Uppercase
Func<string, string> convert = Uppercase;
Console.WriteLine(convert("test"));

string Uppercase(string s) {
  return s.ToUpper();
}

// Declare and invoke Func using a
lambda expression
Console.WriteLine(new Func<int, int>(num => num
+ 1)(2));

// Pass lamba expression as an
argument
TestValues((x, y) => x % y == 0);

void TestValues(Func<int, int,
bool> f) {
  if (f(8, 4))
    Console.WriteLine("true");
  else
    Console.WriteLine("false");
}

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

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

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);

void MyButton_Click(object sender,
System.EventArgs e) { 
  MessageBox.Show(this, "Button was clicked",
"Info", 
    MessageBoxButtons.OK, MessageBoxIcon.Information); 
}

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

‘ Same thing using lamba expression
results = nums.Where(Function(n) n > 4)

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

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

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 a list of students ordered 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

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

// Same thing using lamba expression
results = nums.Where(n => n > 4);

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

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

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 a list of students ordered 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

‘ Attribute can only be applied to classes or structs
<AttributeUsage(AttributeTargets.Class Or
AttributeTargets.Struct)>
Public Class AuthorAttribute
    Inherits Attribute

Public Property Name As String
    Public Property Version As Integer = 0

Public Sub New(ByVal name As String)
        Me.Name = name
    End Sub
End Class

<Author("Sue", Version:=3)>
Class Shape

<IsTested()>
    Sub Move()
        ‘ Do
something...
    End Sub
End Class

// Attribute can only be applied to classes or
structs
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct)]
public class AuthorAttribute : Attribute {

public string Name { get; set; }
    public int Version { get; set; }

public AuthorAttribute(string name) {
        Name = name;
        Version = 0;
    }
}

[Author("Sue", Version = 3)]
class Shape {

[IsTested]
    void Move() {
        // Do
something...
    }
}

Dim c As Integer 
c = Console.Read()    ‘ Read
single char 
Console.WriteLine(c)   ‘ Prints
65 if user enters "A"

int c = Console.Read();  // Read
single char
Console.WriteLine(c);    //
Prints 65 if user enters "A"

‘ 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()

// 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();