VB.NET and C# Comparison
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' Single line only Rem Single line only |
// Single line |
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Value Types Reference Types Dim x As Integer ' Type conversion |
Value Types Reference Types int x;
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Const MAX_STUDENTS As Integer = 25
' Can set to a const or var; may be initialized in a constructor |
const int MAX_STUDENTS = 25;
// Can set to a const or var; may be initialized in a constructor |
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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) ' Prints "Stop is 1" Console.WriteLine(Status.Pass) ' Prints 70 Console.WriteLine(Status.Pass.ToString()) ' Prints 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); // Prints "Stop is 1" Console.WriteLine((int) Status.Pass); // Prints 70 Console.WriteLine(Status.Pass); // Prints Pass |
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Comparison Arithmetic Assignment Bitwise Logical Note: AndAlso and OrElse perform short-circuit logical evaluations String Concatenation |
Comparison Arithmetic Assignment Bitwise Logical Note: && and || perform short-circuit logical evaluations String Concatenation |
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greeting = IIf (age < 20, "What's up?", "Hello") ' One line doesn't require "End If" ' Use : to put two commands on same line ' Preferred ' To break up any long single line use _ ' If x > 5 Then Select Case color ' Must be a primitive data type |
greeting = age < 20 ? "What's up?" : "Hello"; if (age < 20) // Multiple statements must be enclosed in {} No need for _ or : since ; is used to terminate each statement.
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' Array or collection looping ' Breaking out of loops ' Continue to next iteration |
Pre-test Loops:
// no "until" keyword
// Breaking out of loops // Continue to next iteration |
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Dim nums () As Integer = {1, 2, 3}
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int [] nums = {1, 2, 3}; float [,] twoD = new float[rows, cols]; int [][] jagged = new int[3][] { |
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' Pass by value (in, default), reference (in/out), and reference (out) Dim a = 1, b = 1, c As Integer ' c set to zero by default ' Accept variable number of arguments ' Optional parameters must be listed last and must have a default value |
// 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 // Accept variable number of arguments 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. */ |
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Special character constants ' String concatenation (use & or +) ' Chars ' No string literal operator ' String comparison Console.WriteLine(mascot.Substring(2, 3)) ' Prints "son" ' String matching ' My birthday: Oct 12, 1973 ' Mutable string |
Escape sequences // String concatenation // Chars // String literal // String comparison Console.WriteLine(mascot. Substring (2, 3)); // Prints "son" // String matching // My birthday: Oct 12, 1973 // Mutable string |
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' Throw an exception ' Catch an exception ' Deprecated unstructured error handling |
// Throw an exception // Catch an exception |
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Namespace Harding.Compsci.Graphics ' or Namespace Harding Imports Harding.Compsci.Graphics |
namespace Harding.Compsci.Graphics { // or namespace Harding { using Harding.Compsci.Graphics; |
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Accessibility keywords ' Inheritance ' Interface definition // Extending an interface // Interface implementation |
Accessibility keywords // Inheritance
// Extending an interface
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Class SuperHero Private _powerLevel As Integer Public Sub New () _powerLevel = 0 End Sub Public Sub New (ByVal powerLevel As Integer) Me._powerLevel = powerLevel End Sub Protected Overrides Sub Finalize () ' Desctructor code to free unmanaged resources MyBase.Finalize() End Sub End Class |
class SuperHero { |
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Dim hero As SuperHero = New SuperHero With hero hero.Defend("Laura Jones") Dim hero2 As SuperHero = hero ' Both reference the same object hero = Nothing ' Free the object If hero Is Nothing Then _ Dim obj As Object = New SuperHero ' Mark object for quick disposal |
SuperHero hero = new SuperHero(); // No "With" construct hero.Defend("Laura Jones");
hero = null ; // Free the object if (hero == null ) Object obj = new SuperHero(); using (StreamReader reader = File.OpenText("test.txt")) { string line; while ((line = reader.ReadLine()) != null) Console.WriteLine(line); } |
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Structure StudentRecord Dim stu As StudentRecord = New StudentRecord("Bob", 3.5) |
struct StudentRecord { public string name; public float gpa; public StudentRecord(string name, float gpa) { this.name = name; this.gpa = gpa; } } StudentRecord stu = new StudentRecord("Bob", 3.5f); |
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Private _size As Integer foo.Size += 1 |
private int _size; public int Size { get { return _size; } set { if (value < 0) _size = 0; else _size = value; } }
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Delegate Sub MsgArrivedEventHandler(ByVal message As String) Event MsgArrivedEvent As MsgArrivedEventHandler ' or to define an event which declares a delegate implicitly AddHandler MsgArrivedEvent, AddressOf My_MsgArrivedCallback Imports System.Windows.Forms Dim WithEvents MyButton As Button ' WithEvents can't be used on local variable Private Sub MyButton_Click(ByVal sender As System.Object, _ |
delegate void MsgArrivedEventHandler(string message); event MsgArrivedEventHandler MsgArrivedEvent; // Delegates must be used with events in C#
Button MyButton = new Button(); private void MyButton_Click(object sender, System.EventArgs e) { |
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Console.Write("What's your name? ") |
Console.Write("What's your name? ");
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Imports System.IO ' Write out to text file ' Read all lines from text file ' Write out to binary file
' Read from binary file |
using System.IO; // Write out to text file // Read all lines from text file // Write out to binary file // Read from binary file |
VB支持Module,是一种全部成员都是静态的特殊类型
C#支持static class,和VB的Module类似;
VB的Imports语句可以把类的静态成员导入,而C#的using语句没有这个功能
Imports System.Math
VB可以选择变量是否必须声明,以及类型是否必须指定(通过Option语句)
C#则默认是VB最严格的状态
C#可以使用extern alias指定程序集的别名,并使用别名限定运算符::来解析类名冲突的两个程序集
VB没有这个功能,但可以用Global关键字获得命名空间级别名称冲突解析能力
C#可以指定友元程序集,VB不支持
//成员层
VB可以直接重写Object.Finalize方法,而C#必须采用析构函数的语法
C#可以指定attribute的target以便清楚地放置attribute,而VB则通过尖括号的位置来决定,有时候写不出某种C#可行的语法
VB能够重载这些C#不支持的运算符:&, ^, Like, \
C#能够重载这些VB不支持的运算符:++, --, !
VB中子类的构造函数,先调用父类的构造函数,然后才初始化子类的字段
C#中子类的构造函数,先初始化子类的字段,然后才调用父类的构造函数
VB的Implemnts语句可以为实现接口的方法改名,改变访问级别
C#不支持但是有一个显式实现的语法可以帮忙
VB的函数重载,子类和父类的方法视为同级
C#的函数重载,子类优先于父类
VB的Main函数自动加
//继续成员层
C#的自定义event可以修改add和remove的规则
VB的自定义Event除了C#的之外,还支持重载RaiseEvent语句的用法
VB的Event可以直接书写Event参数,自动生成Delegate类型
C#的event必须指定delegate类型
VB不仅支持WithEvents/Handles静态事件绑定语法,也支持AddHandler动态绑定方法
C#的事件只支持使用+=动态绑定
VB的属性(Property)可以带参数
C#的属性不能带参数
尽管不支持手工定义,VB支持属性按引用传递值,C#不支持
VB可以指定一个带有参数的属性为Default,于是支持索引语法
C#则必须把这个东西声明为索引器,即this语法
VB允许方法带有若干可选参数(Optional)可指定默认值
C#不允许
C#支持out参数,传入前不需要初始化
VB不内置支持
C#支持类中使用fixed buffer,即固定大小的类似数组的成员
VB不支持
C#支持按照参数是否带有ref/out进行函数重载
VB不支持这种重载
C#允许仅大小写区分的两个函数或变量存在
VB不区分大小写,因此也不允许大小写不同的两个函数或变量存在
(成员层一时想不起来了,呆会再想)
//函数层
VB支持局部Static变量
C#不支持
VB支持数组的最后一唯大小可变
C#的数组大小不能改变
VB的Try Catch语句支持Exit Try直接进入Finally
C#无类似语句
VB的Catch可以带When子句,使用.NET的异常filter功能有选择的进行捕获
C#完全不支持这一功能
VB可以使用传统的On Error方法,非结构化地处理异常
C#仅支持结构化
C#支持使用checked语句暂时打开或关闭整数溢出检查
VB仅支持整个项目级别处理
VB支持使用函数名作为返回变量,也支持Return
C#只支持Return
VB的Try, Using, For, For Each等语句支持使用前边定义的变量
C#的对应语句只能在语句开始处定义
C#可以支持unsafe语法有限地支持指针和stack数据的访问
VB不支持
C#支持yield return语法的迭代器生成
VB不支持
C#支持delegate语句就地生成支持closure的匿名方法
VB不支持
C#支持在委托与方法结合的过程中使用协变和反边规则
VB则只能使用完全匹配规则
VB和C#的循环和分支有若干次要差别
C#支持nullable类型的运算符跨类型支持
VB需要手工完成同样功能
VB支持用实例访问类的静态成员
C#只支持类明访问
VB支持按照非虚函数的规则,调用自身类型定义的一个虚函数
C#不支持这一功能
类库层
VB有一个非常好用Microsoft.VisualBasic.dll,实现了许多帮助函数,Application Framework应用程序框架,My命名空间等
C#只能望眼欲穿了……
C#以out/ref或者大小写区分不同函数,这就是不符合CLS的。
VB的每个特性几乎都是CLS兼容的(即使是那些C#不支持的),在VB中使用不会从根本上影响到与C#的交互
语言新特性 |
Visual Basic8.0 |
C#2.0 |
Generics(泛型) |
Yes |
Yes |
Iterators(迭代器) |
No |
Yes |
Anonymous methods(匿名方法) |
No |
Yes |
Operator Overloading(运算符重载) |
Yes |
Yes (already present) |
Partial Classes(不完全类) |
Yes |
Yes |
XML documentation(XML文档) |
Yes |
Yes (already present) |
Static Classes(静态类) |
No |
Yes |
Property Accessor Accessibility 属性访问器的可访问性 |
Yes |
Yes |
Namespace Alias Qualifier 名称空间别名限定 |
Yes |
Yes |
Unsigned Types 无符号类型 |
Yes |
Yes (already present)
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Default Instances 默认实例 |
Yes |
No |
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