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};