C#和VB.net语法对比图

comments

vb.net

'single line onlyrem single line only

c#

// single line/* multipleline *//// xml comments on single line/** xml comments on multiple lines */

data types

vb.net

'value typesbooleanbytechar (example: "a")short, integer, longsingle, doubledecimaldate 'reference typesobjectstringdim x as integersystem.console.writeline(x.gettype())system.console.writeline(typename(x)) 'type conversiondim d as single = 3.5dim i as integer = ctype (d, integer)i = cint (d)i = int(d)

c#

//value typesboolbyte, sbytechar (example: 'a')short, ushort, int, uint, long, ulongfloat, doubledecimaldatetime //reference typesobjectstringint x;console.writeline(x.gettype())console.writeline(typeof(int)) //type conversionfloat d = 3.5;int i = (int) d

constants

vb.net

const max_authors as integer = 25readonly 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  forwardend enumenum status   flunk = 50   pass = 70   excel = 90end enumdim a as action = action.stop if a <> action.start then _'prints "stop is 1"    system.console.writeline(a.tostring & " is " & a)'prints 70system.console.writeline(status.pass)'prints passsystem.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 70system.console.writeline((int) status.pass); // prints passsystem.console.writeline(status.pass);

operators

vb.net

'comparison=  <  >  <=  >=  <> 'arithmetic+  -  *  /mod  (integer division)^  (raise to a power) 'assignment=  +=  -=  *=  /=  =  ^=  <<=  >>=  &= 'bitwiseand  andalso  or  orelse  not  <<  >> 'logicaland  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 lineif x <> 100 and y < 5 then x *= 5 : y *= 2   'preferredif x <> 100 and y < 5 then  x *= 5  y *= 2end 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 -= yelse  x /= yend if 'must be a primitive data typeselect case color     case "black", "red"    r += 1  case "blue"    b += 1  case "green"    g += 1  case else    other += 1end 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 stringswitch (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 += 1end while do until c = 10  c += 1loop 'post-test loop:do while c < 10  c += 1loop for c = 2 to 10 step 2  system.console.writeline(c)next 'array or collection loopingdim 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 loopingstring[] 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 elementsdim names(4) as stringnames(0) = "steven"'throws system.indexoutofrangeexceptionnames(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) = 4.5dim 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 arraystring[] names = new string[5];names[0] = "steven";// throws system.indexoutofrangeexceptionnames[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 = 5end sub 'c set to zero by defaultdim a = 1, b = 1, c as integertestfunc(a, b, c)system.console.writeline("{0} {1} {2}", a, b, c) '1 2 5 'accept variable number of argumentsfunction sum(byval paramarray nums as integer()) as integer  sum = 0  for each i as integer in nums    sum += i  nextend 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 valuesub sayhello(byval name as string,optional byval prefix as string = "")  system.console.writeline("greetings, " & prefix& " " & name)end subsayhello("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 initializingtestfunc(a, ref b, out c);system.console.writeline("{0} {1} {2}", a, b, c); // 1 2 5 // accept variable number of argumentsint 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 handlingon 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 / ycatch 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 namespaceend 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 keywordspublicprivatefriendprotectedprotected friendshared 'inheritanceclass articles  inherits authors  ...end class 'interface definitioninterface iarticle   ...end interface 'extending an interfaceinterface iarticle  inherits iauthor  ...end interface 'interface implementation</span>class publicationdate  implements</strong> iarticle, irating   ...end class

c#

//accessibility keywordspublicprivateinternalprotectedprotected internalstatic //inheritanceclass articles: authors {  ...} //interface definitioninterface iarticle {  ...} //extending an interfaceinterface iarticle: iauthor {  ...} //interface implementationclass 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 subend 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 topauthorwith author  .name = "steven"  .authorranking = 3end withauthor.rank("scott")author.demote() 'calling shared method'ortopauthor.rank() dim author2 as topauthor = author 'both refer to same objectauthor2.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 topauthorif typeof obj is topauthor then _  system.console.writeline("is a topauthor object.")

c#

topauthor author = new topauthor();//no "with" constructauthor.name = "steven";author.authorranking = 3; author.rank("scott");topauthor.demote() //calling static method topauthor author2 = author //both refer to same objectauthor2.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 subend structure dim author as authorrecord = new authorrecord("steven", 8.8)dim author2 as authorrecord = authorauthor2.name = "scott"system.console.writeline(author.name) 'prints stevensystem.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 = authorauthor.name = "scott";systemconsole.writeline(author.name); //prints stevensystem.console.writeline(author2.name); //prints scott

properties

vb.net

private _size as integerpublic 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 setend 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 messageas string) event msgarrivedevent as msgarrivedeventhandler 'or to define an event which declares a'delegate implicitlyevent msgarrivedevent(byval message as string) addhandler msgarrivedevent, addressof my_msgarrivedcallback'won't throw an exception if obj is nothingraiseevent msgarrivedevent("test message")removehandler msgarrivedevent, addressof my_msgarrivedcallbackimports system.windows.forms 'withevents can't be used on local variabledim withevents mybutton as buttonmybutton = 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 nullmsgarrivedevent("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 constantsvbcrlf, vbcr, vblf, vbnewlinevbnullstringvbtabvbbackvbformfeedvbverticaltab""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)'orsystem.console.writeline(name & " is " & age & " years old.")dim c as integerc = system.console.read() 'read single charsystem.console.writeline(c) 'prints 65 if user enters "a"

c#

//escape sequencesn, rt 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);//orsystem.console.writeline(name + " is " + 
 age + " years old."); int c = system.console.read(); //read single charsystem.console.writeline(c); 
//prints 65 if user enters "a"

file i/o

vb.net

imports system.io 'write out to text filedim writer as streamwriter = file.createtext  ("c:myfile.txt")writer.writeline("out to file.")writer.close() 'read all lines from text filedim 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 whilereader.close() 'write out to binary filedim str as string = "text data"dim num as integer = 123dim binwriter as new binarywriter(file.openwrite  ("c:myfile.dat"))binwriter.write(str)binwriter.write(num)binwriter.close() 'read from binary filedim 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 filestreamwriter writer = file.createtext  ("c:myfile.txt");writer.writeline("out to file.");writer.close(); //read all lines from text filestreamreader 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 filestring 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 filebinaryreader binreader = new binaryreader(file.openread  ("c:myfile.dat"));str = binreader.readstring();num = binreader.readint32();binreader.close();