在C#中创建类型

重载构造函数:

using System;

public class Wine

{

  public decimal Price;

  public int Year;

  public Wine (decimal price) { Price = price; }

  public Wine (decimal price, int year) : this (price) { Year = year; }

}

对象初始化:

public class Bunny

{

  public string Name;

  public bool LikesCarrots;

  public bool LikesHumans;

  public Bunny () {}

  public Bunny (string n) { Name = n; }

}

Bunny b1 = new Bunny { Name="Bo", LikesCarrots=true, LikesHumans=false };

Bunny b2 = new Bunny ("Bo")     { LikesCarrots=true, LikesHumans=false };

this引用:

public class Panda

{

  public Panda Mate;

  public void Marry (Panda partner)

  {

    Mate = partner;

    partner.Mate = this;

  }

}

public class Test

{

  string name;

  public Test (string name) { this.name = name; }

}

属性:

public class Stock

{

  decimal currentPrice;           // The private "backing" field

  public decimal CurrentPrice     // The public property

  {

     get { return currentPrice; } set { currentPrice = value; }

  }

}

只读和已计算属性:

public class Stock

{

  string  symbol;

  decimal purchasePrice, currentPrice;

  long    sharesOwned;

  public Stock (string symbol, decimal purchasePrice, long sharesOwned)

  {

    this.symbol = symbol;

    this.purchasePrice = currentPrice = purchasePrice;

    this.sharesOwned = sharesOwned;

  }

  public decimal CurrentPrice  { get { return currentPrice;             }

                                 set { currentPrice = value;            } }

  public string Symbol         { get { return symbol;                   } }

  public decimal PurchasePrice { get { return purchasePrice;            } }

  public long    SharesOwned   { get { return sharesOwned;              } }

  public decimal Worth         { get { return CurrentPrice*SharesOwned; } }

}

class Test

{

  static void Main()

  {

    Stock msft = new Stock ("MSFT", 20, 1000);

    Console.WriteLine (msft.Worth);                // 20000

    msft.CurrentPrice = 30;

    Console.WriteLine (msft.Worth);                // 30000

  }

}

自动属性:

public class Stock

{

  // ...

  public decimal CurrentPrice { get; set; }

}

get 和 set 访问:

public class Foo

{

  private decimal x;

  public decimal X

  {

    get          {return x;}

    internal set {x = value;}

  }

}

实现索引:

public class Portfolio

{

  Stock[] stocks;

  public Portfolio (int numberOfStocks)

  {

    stocks = new Stock [numberOfStocks];

  }

  public int NumberOfStocks { get { return stocks.Length; } }

  public Stock this [int index]      // indexer

  {

    get { return stocks [index];  }

    set { stocks [index] = value; }

  }

}

class Test

{

  static void Main()

  {

    Portfolio portfolio = new Portfolio(3);

    portfolio [0] = new Stock ("MSFT", 20, 1000);

    portfolio [1] = new Stock ("GOOG", 300, 100);

    portfolio [2] = new Stock ("EBAY", 33, 77);

    for (int i = 0; i < portfolio.NumberOfStocks; i++)

      Console.WriteLine (portfolio[i].Symbol);

  }

}

多索引:

public class Portfolio

{

  ...

  public Stock this[string symbol]

  {

    get

    {

      foreach (Stock s in stocks)

        if (s.Symbol == symbol)

          return s;

      return null;

    }

  }

}

静态构造函数:

class Test

{

  static Test()

  {

    Console.WriteLine ("Type Initialized");

  }

}

Partial方法:

// PaymentFormGen.cs — auto-generated

partial class PaymentForm

{

  // ...

  partial void ValidatePayment(decimal amount);

}

// PaymentForm.cs — hand-authored

partial class PaymentForm

{

  // ...

  // partial void ValidatePayment(decimal amount)

  {

    if (amount > 100)

    {

      // ...

    }

  }

}

继承:

public class Asset

{

  public string  Name;

  public decimal PurchasePrice, CurrentPrice;

}

public class Stock : Asset   // inherits from Asset

{

  public long SharesOwned;

}

public class House : Asset   // inherits from Asset

{

  public decimal Mortgage;

}

class Test

{

  static void Main()

  {

    Stock msft = new Stock()

    { Name="MSFT", PurchasePrice=20, CurrentPrice=30, SharesOwned=1000 };

    House mansion = new House

    { Name="McMansion", PurchasePrice=300000, CurrentPrice=200000,

      Mortgage=250000 };

    Console.WriteLine (msft.Name);           // MSFT

    Console.WriteLine (mansion.Name);        // McMansion

    Console.WriteLine (msft.SharesOwned);    // 1000

    Console.WriteLine (mansion.Mortgage);    // 250000

  }

}

多态:

class Test

{

  static void Main()

  {

    Stock msft    = new Stock ... ;

    House mansion = new House ... ;

    Display (msft);

    Display (mansion);

  }

  public static void Display (Asset asset)

  {

    System.Console.WriteLine (asset.Name);

  }

}

static void Main() { Display (new Asset()); }    // Compile-time error

public static void Display (House house)         // Will not accept Asset

{

  System.Console.WriteLine (house.Mortgage);

}

向下转换:

Stock msft = new Stock();

Asset a = msft;                      // upcast

Stock s = (Stock)a;                  // downcast

Console.WriteLine (s.SharesOwned);   // <No error>

Console.WriteLine (s == a);          // true

Console.WriteLine (s == msft);       // true

虚拟函数成员:

public class Asset

{

  ...

  public virtual decimal Liability { get { return 0; } }

}

public class Stock : Asset { ... }

public class House : Asset

{

  ...

  public override decimal Liability { get { return Mortgage; } }

}

House mansion = new House

 { Name="McMansion", PurchasePrice=300000, CurrentPrice=200000,

   Mortgage=250000 };

Asset a = mansion;

decimal d2 = mansion.Liability;      // 250000

抽象类和抽象成员:

public abstract class Asset

{

  ...

  public abstract decimal NetValue { get; }   // Note empty implementation

}

public class Stock : Asset

{

  ...                                     // Override an abstract method

  public override decimal NetValue        // just like a virtual method.

  {

    get { return CurrentPrice * SharesOwned; }

  }

}

public class House : Asset     // Every non abstract subtype must

{                              // define NetValue.

  ...

  public override decimal NetValue

  {

    get { return CurrentPrice - Mortgage; }

  }

}

new 和 virtual

public class BaseClass

{

  public virtual void Foo()  { Console.WriteLine ("BaseClass.Foo"); }

}

public class Overrider : BaseClass

{

  public override void Foo() { Console.WriteLine ("Overrider.Foo"); }

}

public class Hider : BaseClass

{

  public new void Foo()      { Console.WriteLine ("Hider.Foo"); }

}

Overrider o = new Overrider();

BaseClass b1 = o;

o.Foo();                           // Overrider.Foo

b1.Foo();                          // Overrider.Foo

Hider h = new Hider();

BaseClass b2 = h;

h.Foo();                           // Hider.Foo

b2.Foo();                          // BaseClass.Foo

GetType() 和 typeof

using System;

public class Point {public int X, Y;}

class Test

{

  static void Main()

  {

    Point p = new Point();

    Console.WriteLine (p.GetType().Name);             // Point

    Console.WriteLine (typeof (Point).Name);          // Point

    Console.WriteLine (p.GetType() == typeof(Point)); // True

    Console.WriteLine (p.X.GetType().Name);           // Int32

    Console.WriteLine (p.Y.GetType().FullName);       // System.Int32

  }

}

显式接口实现:

interface I1 { void Foo(); }

interface I2 { int Foo(); }

public class Widget : I1, I2

{

  public void Foo ()

  {

    Console.WriteLine ("Widget's implementation of I1.Foo");

  }

  int I2.Foo ()

  {

    Console.WriteLine ("Widget's implementation of I2.Foo");

    return 42;

  }

}

Widget w = new Widget();

w.Foo();                      // Widget's implementation of I1.Foo

((I1)w).Foo();                // Widget's implementation of I1.Foo

((I2)w).Foo();                // Widget's implementation of I2.Foo

虚拟地实现接口成员:

public interface IUndoable { void Undo(); }

public class TextBox : IUndoable

{

  public virtual void Undo()

  {

     Console.WriteLine ("TextBox.Undo");

  }

}

public class RichTextBox : TextBox

{

  public override void Undo()

  {

    Console.WriteLine ("RichTextBox.Undo");

  }

}

RichTextBox r = new RichTextBox();

r.Undo();                          // RichTextBox.Undo

((IUndoable)r).Undo();             // RichTextBox.Undo

((TextBox)r).Undo();               // RichTextBox.Undo

在子类中重新实现一个接口:

public interface IUndoable { void Undo(); }

public class TextBox : IUndoable

{

  void IUndoable.Undo() { Console.WriteLine ("TextBox.Undo"); }

}

public class RichTextBox : TextBox, IUndoable

{

  public new void Undo() { Console.WriteLine ("RichTextBox.Undo"); }

}

RichTextBox r = new RichTextBox();

r.Undo();                 // RichTextBox.Undo      Case 1

((IUndoable)r).Undo();    // RichTextBox.Undo      Case 2

public class TextBox : IUndoable

{

  public void Undo() { Console.WriteLine ("TextBox.Undo"); }

}

RichTextBox r = new RichTextBox();

r.Undo();                 // RichTextBox.Undo      Case 1

((IUndoable)r).Undo();    // RichTextBox.Undo      Case 2

((TextBox)r).Undo();      // TextBox.Undo          Case 3

替代接口重新实现:

public class TextBox : IUndoable

{

  void IUndoable.Undo()         { Undo(); }   // Calls method below

  protected virtual void Undo() { Console.WriteLine ("TextBox.Undo"); }

}

public class RichTextBox : TextBox

{

  protected override void Undo() { Console.WriteLine ("RichTextBox.Undo"); }

}

Flags enums枚举:

[Flags]

public enum BorderSides { Left=1, Right=2, Top=4, Bottom=8 }

BorderSides leftRight = BorderSides.Left | BorderSides.Right;

if ((leftRight & BorderSides.Left) != 0)

   System.Console.WriteLine ("Includes Left");   // Includes Left

string formatted = leftRight.ToString();   // "Left, Right"

BorderSides s = BorderSides.Left;

s |= BorderSides.Right;

Console.WriteLine (s == leftRight);   // True

s ^= BorderSides.Right;               // Toggles BorderSides.Right

Console.WriteLine (s);                // Left

Enum枚举类型安全问题:

static bool IsFlagDefined (Enum e)

{

  decimal d;

  return ! decimal.TryParse(e.ToString(), out d);

}

[Flags]

public enum BorderSides { Left=1, Right=2, Top=4, Bottom=8 }

static void Main()

{

  for (int i = 0; i <= 16; i++)

  {

    BorderSides side = (BorderSides)i;

    Console.WriteLine (IsFlagDefined (side) + " " + side);

  }

}

泛型:

public class Stack<T>

{

  int position;

  T[] data = new T[100];

  public void Push (T obj)        { data[position++] = obj;  }

  public T Pop ()                 { return data[--position]; }

}

Stack<int> stack = new Stack<int>();

stack.Push(5);

stack.Push(10);

int x = stack.Pop();

泛方法:

static void Swap<T> (ref T a, ref T b)

{

  T temp = b;

  a = b;

  b = temp;

}

默认泛值:

static void Zap<T> (T[] array)

{

  for (int i = 0; i < array.Length; i++)

    array[i] = default(T);

}

约束:

static T Max <T> (T a, T b) where T : IComparable<T>

{

  return a.CompareTo (b) > 0 ? a : b;

}

static void Initialize<T> (T[] array) where T : new()

{

  for (int i = 0; i < array.Length; i++)

    array[i] = new T();

}

class Stack<T>

{

  Stack<U> FilteredStack<U>() where U : T {...}

}

泛型和协方差:

class Animal {}

class Bear : Animal {}

public class ZooCleaner

{

  public static void Wash<T> (Stack<T> animals) where T : Animal {}

}

Stack<Bear> bears = new Stack<Bear>();

ZooCleaner.Wash (bears);

自引用泛型声明:

interface IEquatable<T> { bool Equals (T obj); }

public class Balloon : IEquatable<Balloon>

{

  string color;

  int cc;

  public bool Equals (Balloon b)

  {

    if (b == null) return false;

    return b.color == color && b.cc == cc;

  }

}

泛型类型中的静态数据的唯一性:

public class Bob<T> { public static int Count; }

class Test

{

  static void Main()

  {

    Console.WriteLine (++Bob<int>.Count);     // 1

    Console.WriteLine (++Bob<int>.Count);     // 2

    Console.WriteLine (++Bob<string>.Count);  // 1

    Console.WriteLine (++Bob<object>.Count);  // 1

  }

}

对象初始化:

List<int> list = new List<int> {1, 2, 3};

巴特西

在C#中创建类型

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