|
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 + "!");
}
}
} |
|
|
|
' 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> */ |
|
|
|
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 = #12/31/2007 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
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("12/31/2007 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;
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 |
|
|
|
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; |
|
|
|
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 |
|
|
|
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
+ |
|
|
|
' Ternary/Conditional operator (Iff 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
' 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 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
}
|
|
|
|
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
} |
|
|
|
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
// 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; |
|
|
|
' 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"); |
|
|
|
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();
} |
|
|
|
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
...
End Interface
// Extending an interface
Interface IAlarmClock
Inherits IClock
...
End Interface
// Interface implementation
Class WristWatch
Implements IAlarmClock, ITimer
...
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 {
...
}
// Extending an interface
interface IAlarmClock : IClock {
...
}
// Interface implementation
class WristWatch : IAlarmClock, ITimer {
...
}
|
|
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
}
} |
|
|
|
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" 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);
} |
|
|
|
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 |
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 |
|
|
|
' 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);
} |
|
|
|
' 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;
} |
|
|
|
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 |
|
|
|
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"
|
|
|
|
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(); |
浙公网安备 33010602011771号