@H_301_9@
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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 + "!");
}
}
}
C# |
' Single line only
Rem Single line only
// Single line
/* Multiple line *//// XML comments on single line/** XML comments on multiple lines */
C# |
Value Types
Boolean
Byte
Char (example: "A"c)
Short,Integer,Long
Single,Double
Decimal
Date
Reference Types
Object
String
Dim x As Integer
Console.WriteLine(x.GetType()) ' Prints System.Int32
Console.WriteLine(GetType(Integer))
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 CTypeInt' set to 3 (Int function truncates the decimal)
bool
byte,sbyte
char (example: 'A')
short,ushort,int,uint,long,ulong
float,double
decimal
DateTime (not a built-in C# type)
object
string
int x;
Console.WriteLine(x.()); // Prints System.Int32
Console.WriteLine(typeof(int));
Console.WriteLine(x.GetType().Name); // prints Int32
// Type conversion
float d = 3.5f;
int i = (int)d; // set to 3 (truncates decimal)
C# |
Const MAX_STUDENTS 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;
C# |
Enum Action
Start
[Stop] ' Stop is a reserved word
Rewind
Forward
End 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};
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
Comparison Arithmetic Assignment Bitwise Logical Note: AndAlso and OrElse perform short-circuit logical evaluations String Concatenation |
&& and || perform short-circuit logical evaluations
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greeting = IIf(age < 20,"What's up?","Hello") ' One line doesn't require "End If" ' Use : to put two commands on same line x <> 100 And y < 5 x *= 5 : y *= 2 ' Preferred ' To break up any long single line use _ whenYouHaveAReally < longLine And _ ' x > 5 Select Case color ' Must be a primitive data type |
greeting = age < 20 ? "What's up?" "Hello"; if (age < 20) // Multiple statements must be enclosed in {} (x != 100 && y < 5) { No need for _ or : since ; is used to terminate each statement.
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' Array or collection looping ' Breaking out of loops ' Continue to next iteration |
Pre-test Loops: // no "until" keywordwhile (c < 10) Post-test Loop: // Breaking out of loops // Continue to next iteration |
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 = {1,3};
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;
[][] jagged = new int[3][] {
new int[5],new int[2],new int[3] };
jagged[0][4] = 5;
C# |
' Pass by value (in,default),reference (in/out),and reference (out)Sub TestFunc(ByVal x As Integer,ByRef y As Integer,'sans-serif'; font-size:10pt"> 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,c) ' 1 2 5
' Accept variable number of argumentsFunction 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(4,3,1) ' returns 10
' Optional parameters must be listed last and must have a default value
Sub SayHello(ByVal name As String,'sans-serif'; font-size:10pt">Optional ByVal prefix As String = "")
Console.WriteLine("Greetings," & prefix & " " & name)
End Sub
SayHello("Strangelove","Dr.")
SayHello("Madonna")
// Pass by value (in,'sans-serif'; font-size:10pt">
void TestFunc(int x,'sans-serif'; font-size:10pt">ref int y,'sans-serif'; font-size:10pt">out int z) {
x++;
y++;
z = 5;
}
int a = 1,c; // c doesn't need initializing
TestFunc(a,'sans-serif'; font-size:10pt"> b,'sans-serif'; font-size:10pt"> c);
Console.WriteLine("{0} {1} {2}",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(4,1); // 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,"");
}
C# |
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 ToUpper().("BISONS")) Then CompareTo("Bisons") = 0) Then ' true
Console.WriteLine(mascot.Substring(2,3)) ' Prints "son"
' String matching
If ("John 3:16" Like "Jo[Hh]? #:*") Then 'true
Imports System.Text.RegularExpressions ' More powerful than Like
Dim r As New Regex("Jo[hH]. "d:*")
If (r.Match("John 3:16").Success) Then 'true
' My birthday: Oct 12,1973
Dim dt As New DateTime(1973,10,12)
Dim s As String = "My birthday: " & dt.ToString("MMM dd,yyyy")
' Mutable string Dim buffer As New System.Text.StringBuilder("two ")
buffer.Append("three ")
buffer.Insert(0,"one ")
buffer.Replace("two","TWO")
Console.WriteLine(buffer) ' Prints "one TWO three"
Escape sequences
"n,"r
"t
""
""
// String concatenationstring school = "Harding"t";
school = school + "University"; // school is "Harding (tab) University"
// Charschar 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.("Bisons")) ("BISONS")) ("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,'sans-serif'; font-size:10pt">
DateTime dt = new DateTime(1973,12);
string s = "My birthday: " + dt.ToString("MMM dd,yyyy");
// Mutable string
System.Text. buffer = new System.Text.("two ");
buffer.Append("three ");
buffer.Insert(0,"one ");
buffer.Replace("two","TWO");
Console.WriteLine(buffer); // Prints "one TWO three"
C# |
' Throw an exception
Dim ex As New Exception("Something is really wrong.")
Throw ex
' Catch an exceptionTry
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 handlingOn 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 exceptiontry {
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();
}
C# |
Namespace Harding.Compsci.Graphics
...
End Namespace
' or
Harding
Compsci
Graphics
...
End NamespaceEnd Namespace End Namespace
Imports Harding.Compsci.Graphics
namespace Harding.Compsci.Graphics {
...
}
// or
Harding {
Compsci {
Graphics {
...
}
}
}
using Harding.Compsci.Graphics;
C# |
Accessibility keywords
Public
Private
Friend
Protected
Protected Friend
Shared
' InheritanceClass FootballGame
Inherits Competition
...
End Class
' Interface definitionInterface IAlarmClock
...
End Interface
// Extending an interface IAlarmClock
IClock
...
// Interface implementation WristWatch
Implements IAlarmClock,ITimer
...
End Class
public
private
internal
protected
protected internal
static
// Inheritanceclass FootballGame Competition {
...
}
// Interface definitioninterface IAlarmClock {
...
}
IAlarmClock IClock {
...
}
WristWatch
C#Constructors / Destructors
SuperHero
Private _powerLevel As Integer
Public Sub New()
_powerLevel = 0
End Sub
Public Sub (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
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
}
}
Dim hero As SuperHero = New SuperHero With hero hero.Defend("Laura Jones") Dim hero2 As SuperHero = hero ' Both reference the same object hero = Nothing' Free the object If hero Is Then _ Dim obj As Object = New SuperHero ' Mark object for quick disposal |
SuperHero hero = new SuperHero(); // No "With" construct hero.Defend("Laura Jones");
null ; // Free the object if (hero == ) Object obj = new SuperHero(); // Mark object for quick disposal |
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Private _size As Integer foo.Size += 1 |
private int _size;
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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 MsgArrivedEvent(ByVal message As String) AddHandler MsgArrivedEvent,'sans-serif'; font-size:10pt">AddressOf My_MsgArrivedCallback Imports System.Windows.Forms Dim WithEvents MyButton As Button ' WithEvents can't be used on local variable Private Sub MyButton_Click(ByVal sender As System.Object,_ |
delegate void MsgArrivedEventHandler(string message); event MsgArrivedEventHandler MsgArrivedEvent; // Delegates must be used with events in C#
Button MyButton = new Button(); private void MyButton_Click(object sender,System.EventArgs e) { |
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Console.Write("What's your name? ") |
Console.Write("What's your name? ");
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