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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