VB C# 语法对比图 (代码实例)

VB C# 语法对比图 (代码实例)
Comments
VB.NET   'Single line only Rem Single line only	C# // Single line /* Multiple line */ /// XML comments on single line /** XML comments on multiple lines */
Data Types
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)	C#   //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
Constants
VB.NET Const MAX_AUTHORS As Integer = 25 ReadOnly MIN_RANK As Single = 5.00	C# const int MAX_AUTHORS = 25; readonly float MIN_RANKING = 5.00;
Enumerations
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())	C# 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);
Operators
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 &	C#   //Comparison ==  <  >  <=  >=  != //Arithmetic +  -  *  / %  (mod) /  (integer division if both operands are ints) Math.Pow(x, y) //Assignment =  +=  -=  *=  /=   %=  &=  |=  ^=  <<=  >>=  ++  -- //Bitwise &  |  ^   ~  <<  >> //Logical &&  ||   ! //String Concatenation +
Choices
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	C#   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; }
Loops
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	C# //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);
Arrays
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	C#   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;
Functions
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")	C# // 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, " + prefix + " " + name); } void SayHello(string name) {   SayHello(name, ""); }
Exception Handling
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	C# 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 }
Namespaces
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	C#   namespace ASPAlliance.DotNet.Community {   ... } // or namespace ASPAlliance {   namespace DotNet {     namespace Community {       ...     }   } } using ASPAlliance.DotNet.Community;
Classes / Interfaces
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	C#   //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 {    ... }
Constructors / Destructors
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	C#   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   } }
Objects
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.")	C#   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.");
Structs
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	C# 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
Properties
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	C# private int _size; public int Size {   get {     return _size;   }   set {     if (value < 0)       _size = 0;     else       _size = value;   } } foo.Size++;
Delegates / Events
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	C#   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, System.EventArgs e) {   MessageBox.Show(this, "Button was clicked", "Info",     MessageBoxButtons.OK, MessageBoxIcon.Information); }
Console I/O
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"	C#   //Escape sequences n, r t Convert.ToChar(65) //Returns 'A' - equivalent to Chr(num) in VB // or (char) 65 System.Console.Write("What's your name? "); string name = SYstem.Console.ReadLine(); System.Console.Write("How old are you? "); int age = Convert.ToInt32(System.Console.ReadLine()); System.Console.WriteLine("{0} is {1} years old.", name, age); //or System.Console.WriteLine(name + " is " + age + " years old."); int c = System.Console.Read(); //Read single char System.Console.WriteLine(c); //Prints 65 if user enters "A"
File I/O
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()	C#   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();