1. 命名空间引用方法
    C#        通过 命名空间后跟"."来引用.
    C++.NET 通过命名空间后跟"::"来引用
    如: (c#)System.Data .   (c++.net) System::Data
2.生成一个窗体的实例并显示出来
     c++.net:  
     //通过指针操作
          frmAbout* frm = new frmAbout();
          frm->ShowDialog(this);                  
   C#:
          frmAbout  frm = new frmAbout();   //生成对象的实例
          frm.ShowDialog(this);
3.程序的入口点
     c++.net 
      一个应用程序必须而且只能有一个CWinApp派生类的对象,并且只能由该对象来调
   用WinMain()函数。这也对应着一个应用程序只有一个惟一的入口.
   如:
               [System::STAThreadAttribute]
               void __stdcall WinMain()
                 {
       Application::Run(new frmLogin());
                  }
    WinMain函数在调用InitInstance进行初始化完毕后，就调用函数处理消息循环。
    Run函数作为一个循环函数，主要进行消息的处理:Run函数不断地查询应用程序的消
息队列，一旦有消息出现就将其发回给Windows,并由Windows再来调用处理该消息的窗口
函数，而窗口则是隐藏在应用程序框架类内部的。当消息队列中没有消息时（大多数的时
候是这种情况）,Run函数就会调用OnIdle函数，从而做一些应用程序框架类或用户在程序
空闲时所要做的工作。
       如果既没有消息又没有空闲工作要做,那么应用程序就一直处于等待状态.
       当应用程序关闭时,Run函数就会调用ExitInstance函数,做一些退出前的处理工作.  

C#也如此
     如:
     // <summary>
         /// 应用程序的主入口点。
         /// </summary>
         [STAThread]
         static void Main()
         {
                   Application.Run(new frmLogin());
         }        
4.设置(或获取)窗体和相关组件的属性
(下面的实例均基于相同的命名空间)
  c++.net
this->BackColor =System::Drawing::Color::Gold ;
        this->textBox1->Text =this->BackColor.ToString(); 
        this->pictureBox1->BackColor =System::Drawing::Color::Red ;
    C#        
        this.BackColor=System.Drawing.Color.Gold;  //获取或设置本窗体的属性用 this.
        this.textBox1.Text =this.BackColor.ToString();    
        Form2 frm2=new Form2();
        frm2.BackColor=System.Drawing.Color.Gold;  //获取或设置新实例窗体的属性用 新实例名. 
        frm2.ShowDialog(this) ;
        frm2.Close();
                this.pictureBox1.BackColor = System.Drawing.Color.Red ;

5 .C#和VB.net的语法比较
   

C#和VB.net的语法比较
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();

原文链接：https://www.cnblogs.com/furenjun/archive/2006/03/28/360848.html