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-generatedpartial class PaymentForm{ // ... partial void ValidatePayment(decimal amount);} // PaymentForm.cs — hand-authoredpartial 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 errorpublic 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; // upcastStock s = (Stock)a; // downcastConsole.WriteLine (s.SharesOwned); //Console.WriteLine (s == a); // trueConsole.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.Foob1.Foo(); // Overrider.FooHider h = new Hider();BaseClass b2 = h;h.Foo(); // Hider.Foob2.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 Leftstring formatted = leftRight.ToString(); // "Left, Right"BorderSides s = BorderSides.Left;s |= BorderSides.Right;Console.WriteLine (s == leftRight); // Trues ^= BorderSides.Right; // Toggles BorderSides.RightConsole.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{ int position; T[] data = new T[100]; public void Push (T obj) { data[position++] = obj; } public T Pop () { return data[--position]; }}
Stack stack = new Stack (); stack.Push(5);stack.Push(10);int x = stack.Pop();
泛方法:
static void Swap(ref T a, ref T b){ T temp = b; a = b; b = temp;}
默认泛值:
static void Zap(T[] array){ for (int i = 0; i < array.Length; i++) array[i] = default(T);}
约束:
static T Max(T a, T b) where T : IComparable { return a.CompareTo (b) > 0 ? a : b;}
static void Initialize(T[] array) where T : new(){ for (int i = 0; i < array.Length; i++) array[i] = new T(); }
class Stack{ Stack FilteredStack() where U : T {...}}
泛型和协方差:
class Animal {}class Bear : Animal {} public class ZooCleaner{ public static void Wash (Stack animals) where T : Animal {}} Stackbears = new Stack ();ZooCleaner.Wash (bears);
自引用泛型声明:
interface IEquatable{ bool Equals (T obj); }public class Balloon : IEquatable { 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{ public static int Count; }class Test{ static void Main() { Console.WriteLine (++Bob .Count); // 1 Console.WriteLine (++Bob .Count); // 2 Console.WriteLine (++Bob .Count); // 1 Console.WriteLine (++Bob
对象初始化:
List list = new List {1, 2, 3};