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VB.NET
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Program Structure
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C#
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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
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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 + "!");
}
}
}
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' Single line only
REM Single line only
''' <summary>XML comments</summary>
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// Single line
/* Multiple
line */
/// <summary>XML comments on single
line</summary>
/** <summary>XML comments on multiple
lines</summary> */
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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)
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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)
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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
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const int MAX_STUDENTS = 25;
// Can set to a const or var; may be initialized in a constructor
readonly float MIN_DIAMETER = 4.93f;
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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
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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
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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
&
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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
+
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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?" Else greeting = "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
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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
}
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Pre-test Loops:
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While c < 10
c += 1
End While
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Do
Until c = 10
c += 1
Loop
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Do While c < 10
c += 1
Loop
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For c = 2 To 10 Step 2
Console.WriteLine(c)
Next
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Post-test Loops:
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Do
c += 1
Loop While c < 10
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Do
c += 1
Loop Until c = 10
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' 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
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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
}
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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
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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;
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' 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("Madonna")
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// 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, "");
}
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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"
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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"
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VB.NET
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Exception
Handling
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C#
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' 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)
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// 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();
}
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Namespace
Harding.Compsci.Graphics
...
End Namespace
' or
Namespace Harding
Namespace
Compsci
Namespace
Graphics
...
End Namespace
End Namespace
End Namespace
Imports
Harding.Compsci.Graphics
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namespace
Harding.Compsci.Graphics {
...
}
// or
namespace Harding {
namespace
Compsci {
namespace
Graphics {
...
}
}
}
using
Harding.Compsci.Graphics;
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VB.NET
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Classes
/ Interfaces
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C#
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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
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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 {
...
}
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VB.NET
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Constructors
/ Destructors
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C#
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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
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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
}
}
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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
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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);
}
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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
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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
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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
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private
int _size;
public int Size {
get {
return _size;
}
set {
if (value < 0)
_size = 0;
else
_size = value;
}
}
foo.Size++;
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VB.NET
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Delegates
/ Events
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C#
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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
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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);
}
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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"
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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"
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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()
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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();
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