Lập trình VB.Net

So sánh sự khác nhau giữa VB.Net và C#

So sánh sự khác nhau giữa VB.Net và C#
Được viết bởi Minh Hoàng

Series lập trình VB.NET, ngôn ngữ lập trình hướng đối tượng .NET Framework

Sau đây chúng ta cùng tìm hiểu một số cách viết khác nhau giữa VB.NetC# trong các xử lý cụ thể:

01. Cấu trúc chương trình
Imports System

Namespace MinhHoangBlog
    Class HelloWorld
        ' Cách truyền tham số cho hàm
        Overloads Shared Sub Main(ByVal args() As String)
            ' Cách khai báo biến và khởi tạo giá trị
            Dim name As String = "VB.NET"

            If args.Length = 1 Then name = args(0)

            ' Cách nối chuỗi
            Console.WriteLine( "Hello, " & name & "!" )
        End Sub
    End Class
End Namespace
using System;

namespace MinhHoangBlog
{
    public class HelloWorld
    {
        // Cách truyền tham số cho hàm
        public static void Main(string[] args)
        {
            // Cách khai báo biến và khởi tạo giá trị
            string name = "C#";

            if (args.Length == 1) name = args[0];

            // Cách nối chuỗi
            Console.WriteLine( "Hello, " + name + "!" );
        }
    }
}
02. Comments code
' Chỉ có comment 1 dòng

' KHÔNG có comment nhiều dòng

''' <summary>Mô tả ý nghĩa của hàm hoặc class,...</summary>
// Comment một dòng

/* Comment
            nhiều dòng  */

/* Comment
 * nhiều dòng
 */

/// <summary>Mô tả ý nghĩa của hàm hoặc class,... một dòng</summary>
/** <summary>Mô tả ý nghĩa của hàm hoặc class,... nhiều dòng</summary> */
03. Namespaces
Namespace WelcomeTo.MinhHoang.Blog
    ' bla bla
End Namespace

' or

Namespace WelcomeTo
    Namespace MinhHoang
        Namespace Blog
            ' bla bla
        End Namespace
    End Namespace
End Namespace

Imports WelcomeTo.MinhHoang.Blog
namespace WelcomeTo.MinhHoang.Blog
{
  // bla bla
}

// or

namespace WelcomeTo
{
    namespace MinhHoang
    {
        namespace Blog
        {
            // bla bla
        }
    }
}

using WelcomeTo.MinhHoang.Blog;
04. Constructors & Destructors
Class SuperHero
    Inherits Person               ' Cách thể hiện thừa kế

    Private powerLevel As Integer
    Private name As String

    ' Constructor mặc định
    Public Sub New()
        powerLevel = 0
        name = "Robin Hood"
    End Sub

    Public Sub New(ByVal powerLevel As Integer)
        Me.New( "Robin Hood" )    ' Gọi constructor của chính nó
        Me.powerLevel = powerLevel
    End Sub

    Public Sub New(ByVal name As String)
        MyBase.New(name)          ' Gọi constructor của base class
        Me.name = name
    End Sub

    Shared Sub New()
        ' Shared constructor được gọi trước khi instance đầu tiên được tạo
    End Sub

    Protected Overrides Sub Finalize()
        ' Destructor Giải phóng tài nguyên không dùng sau khi kết thúc chương trình 
        MyBase.Finalize()
    End Sub
End Class
class SuperHero : Person            // Cách thể hiện thừa kế
{
    private int powerLevel;
    private string name;

    // Constructor mặc định
    public SuperHero()
    {
        powerLevel = 0;
        name = "Robin Hood";
    }

    // Gọi constructor của chính nó
    public SuperHero(int powerLevel) : this( "Robin Hood" )
    {
        this.powerLevel = powerLevel;
    }

    // Gọi constructor của base class
    public SuperHero(string name) : base(name)
    {
        this.name = name;
    }

    static SuperHero()
    {
        // Static constructor được gọi trước khi instance đầu tiên được tạo
    }

    ~SuperHero()
    {
        // Destructor ngầm định tạo ra phương thức Finalize() để giải phóng tài nguyên bộ nhớ
        // trước khi thoát khỏi chương trình
    }
}
05. Nhập xuất (Console I/O)
' Input giá trị nhập vào từ bàn phím
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())

' Output thông tin ra console
Console.WriteLine("{0} is {1} years old.", name, age)
' or 
Console.WriteLine( name & " is " & age & " years old." )

Dim c As Integer = Console.Read()
Console.WriteLine(c)    ' Nếu nhập A thì sẽ hiện ra ở console là 65
/* Input giá trị nhập vào từ bàn phím   */
Console.Write( "What's your name? " );
string name = Console.ReadLine();

Console.Write( "How old are you? " );
int age = Convert.ToInt32(Console.ReadLine());

/* Output thông tin ra console          */
Console.WriteLine("{0} is {1} years old.", name, age);
// or
Console.WriteLine( name + " is " + age + " years old." );

int c = Console.Read();
Console.WriteLine(c);    // Nếu nhập A thì sẽ hiện ra ở console là 65
06. Các toán tử (Operators)
' 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
+
07. Các kiểu dữ liệu và cách khai báo, khởi tạo biến (Data Types)
' Value Types
Boolean
Byte, SByte
Char
Short, UShort, Integer, UInteger, Long, ULong
Single, Double
Decimal
Date                                    ' (alias of System.DateTime)
structures
enumerations

' Reference Types
objects
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 = 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

' 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())          ' System.Int32 
Console.WriteLine(GetType(Integer))     ' System.Int32 
Console.WriteLine(TypeName(x))          ' 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
// Value Types
bool
byte, sbyte
char
short, ushort, int, uint, long, ulong
float, double
decimal
DateTime                    // (not a built-in C# type)
structs
enumerations

// Reference Types
objects
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());             // System.Int32
Console.WriteLine(typeof(int));             // System.Int32 
Console.WriteLine(x.GetType().Name);        // 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
08. Khai báo hằng số (Constants)
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;
09. Kiểu String
' 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"
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))                   ' son
s = Mid("testing", 2, 3)                      ' est

' 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" 
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))              // son
s = "testing".Substring(1, 3);	         // est (no Mid)

// Replacement
s = mascot.Replace( "sons", "nomial" ))  // 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"
10. Kiểu Arrays
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 

// 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;
11. Kiểu enum (Enumerations)
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)   ' "Stop is 1" 

Console.WriteLine(Status.Pass)                  ' 70 
Console.WriteLine(Status.Pass.ToString)         ' 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);    // "Stop is 1"

Console.WriteLine((int) Status.Pass);         // 70 
Console.WriteLine(Status.Pass);               // Pass
12. Kiểu Structs
Structure Student
    Public name As String
    Public age As Integer

    Public Sub New(ByVal name As String, ByVal age As Integer)
        Me.name = name
        Me.age = age
    End Sub
End Structure

Dim std1 As Student = New Student("Peter", 20)
Dim std2 As Student = std1

stu2.name = "Marry"
Console.WriteLine(std1.name)    ' Output: Peter 
Console.WriteLine(std2.name)    ' Output: Marry
struct Student
{
    public string name;
    public int age;

    public Student(string name, int age)
    {
        this.name = name;
        this.age = age;
    }
}
Student std1 = new Student("Peter", 20);
Student std2 = std1;

std2.name = "Marry";
Console.WriteLine(std1.name);   // Output: Peter
Console.WriteLine(std2.name);   // Output: Marry
13. Using Objects
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" 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);
}
14. Câu lệnh điều kiện và switch
' Null-coalescing operator if called with 2 arguments
x = If(y, 5)            ' if y is not Nothing then x = y, else x = 5

' 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
// Null-coalescing operator
x = y ?? 5;   // if y != null then x = y, else x = 5

// 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
}
15. Vòng lặp (Loops)
' 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
}
16. Cách viết hàm (Functions)
' 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" );
17. Regular Expressions
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)Frown\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)Frown\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
18. Xử lý ngoại lệ (Exception Handling)
' 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;

// 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(); 
}
19. Classes & Interfaces
' 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 Team
    ...
    Protected name As String
    Public Overridable Sub DisplayName()
        Console.WriteLine(name)
    End Sub
End Class

' Inheritance
Class FootballTeam
    Inherits Team
    ...
    Public Overrides Sub DisplayName()
        Console.WriteLine( "** " + name + " **" )
    End Sub
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 
// 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 Team
{
    ...
    protected string name;
    public virtual void DislpayName()
    {
        Console.WriteLine(name);
    }

    // Inheritance
    class FootballTeam : Team
    {
    ...
    public override void DislpayName()
        {
            Console.WriteLine( "** " + name + " **" );
        }
    }


    // 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; }
    ...
}
20. Properties
' 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;
    }
}
21. Generics
' 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;
}
22. Collections
' Popular classes In System.Collections (stored As Object)
ArrayList
Hashtable
Queue
Stack

' Popular classes In System.Collections.Generic (stored As type T)
List(Of T)
SortedList(Of TKey, TValue)
Dictionary(Of TKey, TValue)
Queue(Of T)
Stack(Of T)

' Popular classes In System.Collections.Concurrent (thread safe)
BlockingCollection(Of T)
ConcurrentDictionary(Of TKey, TValue)
ConcurrentQueue(Of T)
ConcurrentStack(Of T)

' Microsoft.VisualBasic(Not recommended)
Collection

' Store ID and name
Dim students As New Dictionary(Of Integer, String) From
{
    {123, "Bob"},
    {444, "Sue"},
    {555, "Jane"}
}

students.Add( 987, "Gary" )
Console.WriteLine(students(444))   ' Sue

' Display all
For Each stu In students
    Console.WriteLine(stu.Key & " = " & stu.Value)
Next

' Method iterator for custom iteration over a collection
Iterator Function OddNumbers(ByVal lastNum As Integer) As System.Collections.IEnumerable
    For num = 1 To lastNum
        If num Mod 2 = 1 Then
            Yield num
        End If
    Next
End Function

' 1 3 5 7
For Each num In OddNumbers(7)
Console.Write( num & " " )
Next
// Popular classes in System.Collections (stored as Object)
ArrayList
Hashtable
Queue
Stack

// Popular classes in System.Collections.Generic (stored as type T)
List<T>
SortedList<TKey, TValue>
Dictionary<TKey, TValue>
Queue<T>
Stack<T>

// Popular classes in System.Collections.Concurrent (thread safe)
BlockingCollection<T>
ConcurrentDictionary<TKey, TValue>
ConcurrentQueue<T>
ConcurrentStack<T>

// No equivalent to Microsoft.VisualBasic.Collection

// Store ID and name
var students = new Dictionary<int, string>
{
    { 123, "Bob" },
    { 444, "Sue" },
    { 555, "Jane" }
};

students.Add( 987, "Gary" );
Console.WriteLine(students[444]);   // Output: Sue

// Display all
foreach (var stu in students) {
    Console.WriteLine(stu.Key + " = " + stu.Value);
}

// Method iterator for custom iteration over a collection
static System.Collections.Generic.IEnumerable<int> OddNumbers(int lastNum)
{
    for (var num = 1; num <= lastNum; num++)
        if (num % 2 == 1)
            yield return num;
}

// 1 3 5 7
foreach (double num in OddNumbers(7))
{
    Console.Write( num + " " );
}
23. Delegates & Lambda Expressions
' Khai báo
Delegate Sub HelloDelegate(ByVal s As String)

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
// Khai báo
delegate void HelloDelegate(string s);

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" );
}
24. Phương thức mở rộng (Extension Methods)
Imports System.Runtime.CompilerServices

Module StringExtensions
    <Extension()>
    Public Function VowelCount(ByVal s As String) As Integer
        Return s.Count(Function(c) "aeiou".Contains(Char.ToLower(c)))
    End Function
End Module

' Using the extension method
Console.WriteLine("This is a test".VowelCount)
public static class StringExtensions
{
    public static int VowelCount(this string s)
    {
        return s.Count(c => "aeiou".Contains(Char.ToLower(c)));
    }
}



// Using the extension method
Console.WriteLine("This is a test".VowelCount());
25. Sự kiện (Events)
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

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);

void MyButton_Click(object sender, System.EventArgs e)
{
    MessageBox.Show(this, "Button was clicked", "Info",
                    MessageBoxButtons.OK, MessageBoxIcon.Information);
}
26. LINQ
Dim nums() As Integer = {5, 8, 2, 1, 6}

' 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
int[] nums = { 5, 8, 2, 1, 6 };

// 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
27. Attributes
' Attribute can be applied to anything
Public Class IsTestedAttribute
    Inherits Attribute
End Class

' 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 be applied to anything
public class IsTestedAttribute : Attribute
{
}

// 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...
    }
}
28. File I/O
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();
29. Một số điểm khác nhau khác
■ Về ký tự xuống dòng:

C#:     Environment.NewLine
VB.Net: vbNewLine / vbCrLf / vbCr / vbLf

Các hằng số trong VB ứng với dòng mới gồm:
vbCrLf = “\r\n”
vbCr = “\r”
vbLf = “\n”

■ Đường dẫn file:

VB:     "c:\foo\bar.txt"
C++:    "c:\\foo\\bar.txt"
C#:     giống C++, hoặc @"c:\foo\bar.txt"
Cảm ơn bạn đã theo dõi. Đừng ngần ngại hãy cùng thảo luận với chúng tôi! Minh Hoàng Blog | Nào cùng vui hehe


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Minh Hoàng

Xin chào, tôi là Hoàng Ngọc Minh, hiện đang làm BrSE, tại công ty Toyota, Nhật Bản. Những gì tôi viết trên blog này là những trải nghiệm thực tế tôi đã đúc rút ra được trong cuộc sống, quá trình học tập và làm việc. Các bài viết được biên tập một cách chi tiết, linh hoạt để giúp người đọc có thể tiếp cận một cách dễ dàng nhất. Hi vọng nó sẽ có ích hoặc mang lại một góc nhìn khác cho bạn[…]

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