C#和VB.net的语法相差还是比较大的. 可能你会C#,可能你会VB.
将它们俩放在一起对比一下你就会很快读懂,并掌握另一门语言.
相信下面这张图会对你帮助很大.
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Comments | |
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VB.NET
'Single line only Rem Single line only
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// Single line /* Multiple line */ /// XML comments on single line /** XML comments on multiple lines */ |
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Data Types | |
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VB.NET
'Value Types Boolean Byte Char (example: "A") Short, Integer, Long Single, Double Decimal Date 'Reference Types Object String Dim x As Integer System.Console.WriteLine(x.GetType()) System.Console.WriteLine(TypeName(x)) 'Type conversion Dim d As Single = 3.5 Dim i As Integer = CType (d, Integer) i = CInt (d) i = Int(d)
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//Value Types bool byte, sbyte char (example: 'A') short, ushort, int, uint, long, ulong float, double decimal DateTime //Reference Types object string int x; Console.WriteLine(x.GetType()) Console.WriteLine(typeof(int)) //Type conversion float d = 3.5; int i = (int) d
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Constants | |
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VB.NET Const MAX_AUTHORS As Integer = 25 ReadOnly MIN_RANK As Single = 5.00 |
const int MAX_AUTHORS = 25; readonly float MIN_RANKING = 5.00; |
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Enumerations | |
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VB.NET Enum Action Start 'Stop is a reserved word [Stop] 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 _ 'Prints "Stop is 1" System.Console.WriteLine(a.ToString & " is " & a) 'Prints 70 System.Console.WriteLine(Status.Pass) 'Prints Pass System.Console.WriteLine(Status.Pass.ToString()) |
enum Action {Start, Stop, Rewind, Forward};
enum Status {Flunk = 50, Pass = 70, Excel = 90};
Action a = Action.Stop;
if (a != Action.Start)
//Prints "Stop is 1"
System.Console.WriteLine(a + " is " + (int) a);
// Prints 70
System.Console.WriteLine((int) Status.Pass);
// Prints Pass
System.Console.WriteLine(Status.Pass); |
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Operators | |
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VB.NET
'Comparison = < > <= >= <> 'Arithmetic + - * / Mod (integer division) ^ (raise to a power) 'Assignment = += -= *= /= = ^= <<= >>= &= 'Bitwise And AndAlso Or OrElse Not << >> 'Logical And AndAlso Or OrElse Not 'String Concatenation &
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//Comparison == < > <= >= != //Arithmetic + - * / % (mod) / (integer division if both operands are ints) Math.Pow(x, y) //Assignment = += -= *= /= %= &= |= ^= <<= >>= ++ -- //Bitwise & | ^ ~ << >> //Logical && || ! //String Concatenation +
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Choices | |
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VB.NET
greeting = IIf(age < 20, "What's up?", "Hello") 'One line doesn't require "End If", no "Else" If language = "VB.NET" Then langType = "verbose" '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 'or to break up any long single command use _ If henYouHaveAReally < 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 'Must be a primitive data type Select Case color Case "black", "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 (x != 100 && y < 5)
{
// Multiple statements must be enclosed in {}
x *= 5;
y *= 2;
}
if (x > 5)
x *= y;
else if (x == 5)
x += y;
else if (x < 10)
x -= y;
else
x /= y;
//Must be integer or string
switch (color)
{
case "black":
case "red": r++;
break;
case "blue"
break;
case "green": g++;
break;
default: other++;
break;
}
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Loops | |
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VB.NET
'Pre-test Loops:
While c < 10
c += 1
End While Do Until c = 10
c += 1
Loop
'Post-test Loop:
Do While c < 10
c += 1
Loop
For c = 2 To 10 Step 2
System.Console.WriteLine(c)
Next
'Array or collection looping
Dim names As String() = {"Steven", "SuOk", "Sarah"}
For Each s As String In names
System.Console.WriteLine(s)
Next
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//Pre-test Loops: while (i < 10)
i++;
for (i = 2; i < = 10; i += 2)
System.Console.WriteLine(i);
//Post-test Loop:
do
i++;
while (i < 10);
// Array or collection looping
string[] names = {"Steven", "SuOk", "Sarah"};
foreach (string s in names)
System.Console.WriteLine(s);
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Arrays | |
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VB.NET
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) = "Steven"
'Throws System.IndexOutOfRangeException
names(5) = "Sarah"
'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] = "Steven";
// Throws System.IndexOutOfRangeException
names[5] = "Sarah"
// C# can't dynamically resize an array.
//Just copy into new array.
string[] names2 = new string[7];
// or names.CopyTo(names2, 0);
Array.Copy(names, names2, names.Length);
float[,] twoD = new float[rows, cols];
twoD[2,0] = 4.5;
int[][] jagged = new int[3][] {
new int[5], new int[2], new int[3] };
jagged[0][4] = 5;
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Functions | |
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VB.NET
'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
'c set to zero by default
Dim a = 1, b = 1, c As Integer
TestFunc(a, b, c)
System.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 a 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 = "")
System.Console.WriteLine("Greetings, " & prefix
& " " & name)
End Sub
SayHello("Steven", "Dr.")
SayHello("SuOk")
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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);
System.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) {
System.Console.WriteLine("Greetings, "
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Exception Handling | |
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VB.NET
'Deprecated unstructured error handling
On Error GoTo MyErrorHandler
...
MyErrorHandler: System.Console.WriteLine(Err.Description)
Dim ex As New Exception("Something has really gone wrong.")
Throw ex
Try
y = 0
x = 10 / y
Catch ex As Exception When y = 0 'Argument and When is optional
System.Console.WriteLine(ex.Message)
Finally
DoSomething()
End Try
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Exception up = new Exception("Something is really wrong.");
throw up; // ha ha
try{
y = 0;
x = 10 / y;
}
catch (Exception ex) { //Argument is optional, no "When" keyword
Console.WriteLine(ex.Message);
}
finally{
// Do something
}
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Namespaces | |
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VB.NET
Namespace ASPAlliance.DotNet.Community ... End Namespace 'or Namespace ASPAlliance Namespace DotNet Namespace Community ... End Namespace End Namespace End Namespace Imports ASPAlliance.DotNet.Community
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namespace ASPAlliance.DotNet.Community {
...
}
// or
namespace ASPAlliance {
namespace DotNet {
namespace Community {
...
}
}
}
using ASPAlliance.DotNet.Community;
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Classes / Interfaces | |
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VB.NET
'Accessibility keywords Public Private Friend Protected Protected Friend Shared 'Inheritance Class Articles Inherits Authors ... End Class 'Interface definition Interface IArticle ... End Interface 'Extending an interface Interface IArticle Inherits IAuthor ... End Interface 'Interface implementation</span> Class PublicationDate Implements</strong> IArticle, IRating ... End Class
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//Accessibility keywords
public
private
internal
protected
protected internal
static
//Inheritance
class Articles: Authors {
...
}
//Interface definition
interface IArticle {
...
}
//Extending an interface
interface IArticle: IAuthor {
...
}
//Interface implementation
class PublicationDate: IArticle, IRating {
...
}
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Constructors / Destructors | |
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VB.NET Class TopAuthor Private _topAuthor As Integer Public Sub New() _topAuthor = 0 End Sub Public Sub New(ByVal topAuthor As Integer) Me._topAuthor = topAuthor End Sub Protected Overrides Sub Finalize() 'Desctructor code to free unmanaged resources MyBase.Finalize() End Sub End Class |
class TopAuthor {
private int _topAuthor;
public TopAuthor() {
_topAuthor = 0;
}
public TopAuthor(int topAuthor) {
this._topAuthor= topAuthor
}
~TopAuthor() {
// Destructor code to free unmanaged resources.
// Implicitly creates a Finalize method
}
}
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Objects | |
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VB.NET
Dim author As TopAuthor = New TopAuthor
With author
.Name = "Steven"
.AuthorRanking = 3
End With
author.Rank("Scott")
author.Demote() 'Calling Shared method
'or
TopAuthor.Rank()
Dim author2 As TopAuthor = author 'Both refer to same object
author2.Name = "Joe"
System.Console.WriteLine(author2.Name) 'Prints Joe
author = Nothing 'Free the object
If author Is Nothing Then _
author = New TopAuthor
Dim obj As Object = New TopAuthor
If TypeOf obj Is TopAuthor Then _
System.Console.WriteLine("Is a TopAuthor object.")
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TopAuthor author = new TopAuthor();
//No "With" construct
author.Name = "Steven";
author.AuthorRanking = 3;
author.Rank("Scott");
TopAuthor.Demote() //Calling static method
TopAuthor author2 = author //Both refer to same object
author2.Name = "Joe";
System.Console.WriteLine(author2.Name) //Prints Joe
author = null //Free the object
if (author == null)
author = new TopAuthor();
Object obj = new TopAuthor();
if (obj is TopAuthor)
SystConsole.WriteLine("Is a TopAuthor object.");
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Structs | |
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VB.NET
Structure AuthorRecord
Public name As String
Public rank As Single
Public Sub New(ByVal name As String, ByVal rank As Single)
Me.name = name
Me.rank = rank
End Sub
End Structure
Dim author As AuthorRecord = New AuthorRecord("Steven", 8.8)
Dim author2 As AuthorRecord = author
author2.name = "Scott"
System.Console.WriteLine(author.name) 'Prints Steven
System.Console.WriteLine(author2.name) 'Prints Scott
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struct AuthorRecord {
public string name;
public float rank;
public AuthorRecord(string name, float rank) {
this.name = name;
this.rank = rank;
}
}
AuthorRecord author = new AuthorRecord("Steven", 8.8);
AuthorRecord author2 = author
author.name = "Scott";
SystemConsole.WriteLine(author.name); //Prints Steven
System.Console.WriteLine(author2.name); //Prints Scott
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Properties | |
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VB.NET
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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Delegates / Events | |
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VB.NET
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
'WithEvents can't be used on local variable
Dim WithEvents MyButton As Button
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); //Throws exception if obj is null MsgArrivedEvent("Test message"); 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,
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Console I/O | |
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VB.NET
'Special character constants
vbCrLf, vbCr, vbLf, vbNewLine
vbNullString
vbTab
vbBack
vbFormFeed
vbVerticalTab
""
Chr(65) 'Returns 'A'
System.Console.Write("What's your name? ")
Dim name As String = System.Console.ReadLine()
System.Console.Write("How old are you? ")
Dim age As Integer = Val(System.Console.ReadLine())
System.Console.WriteLine("{0} is {1} years old.", name, age)
'or
System.Console.WriteLine(name & " is " & age & " years old.")
Dim c As Integer
c = System.Console.Read() 'Read single char
System.Console.WriteLine(c) 'Prints 65 if user enters "A"
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//Escape sequences n, r t Convert.ToChar(65)
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File I/O | |
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VB.NET
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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