第3章面向对象技术

1、第五讲 代表 事件和索引指示器5.1使用索引器索引器能够将索引用于对象来获得该对象所存储的值。定义格式：Public 数据类型 thisint index Get 想返回的值Set 想赋予的值修饰符有：l newl publicl protectedl internall privatel virtuall sealedl overridel abstract例如 下面的例子用于打印出小组人员的名单程序清单 using Systemclass Teamstring s_name = new string8;public string thisint nIndexGetreturn s_name

2、nIndex;Sets_namenIndex = value;class Testpublic static void Main()Team t1 = new Team();for(int i=0; i8 ;i+)Console.WriteLine(t1i);根据域名解析 IP 地址程序清单 using System;using System.Net;class ResolveDNSIPAddress m_arrayIPs;Public void Resolve(string s_host)IPHostEntry ip = DNS.GetHostByName(s_host);m_arrayIP

3、s = ip.AddressList;public IPAddress thisint nIndexGetreturn m_arrayIPsnIndex;public int IPLengthGetreturn m_arrayIPs.Length;class TestApppublic static void Main()ResolveDNS resolver1 = new ResolveDNS();resolver1.Resolve();int n = resolver1.IPLength;Console.WriteLine(“Get the IP Address o

4、f the host”);Console.WriteLine();for(int i=0;isecond) Int temp=first; First=second; Second=temp; 2)、public static void Descending (ref int first,ref int second) If(first second ) int tmp = first; first = second; second = tmp; public static void Descending( ref int first, ref int second ) if (first s

5、econd ) int tmp = first; first = second; second = tmp; public static void Main() SortClass.Sort up = new SortClass.Sort(Ascending); /创建代表对象 SortClass.Sort down = new SortClass.Sort(Descending); SortClass doIT = new SortClass(); /创建sortclass对象 SortClass.val1 = 310; /设置排序变量 SortClass.val2 = 220; Conso

6、le.WriteLine(Before Sort: val1 = 0, val2 = 1, SortClass.val1, SortClass.val2); doIT.DoSort(up); /调用dosort方法 Console.WriteLine(After Sort: val1 = 0, val2 = 1, SortClass.val1, SortClass.val2); Console.WriteLine(Before Sort: val1 = 0, val2 = 1, SortClass.val1, SortClass.val2); doIT.DoSort(down); Consol

7、e.WriteLine(After Sort: val1 = 0, val2 = 1, SortClass.val1, SortClass.val2); 5.3 事件形象地说， 事件 event 就是类或对象用来“发出通知” 的成员， 通过提供事件的句柄，客户能够把事件和可执行代码联系在一起。事件是类发出的通知，指出了发生某种事情。这样其他类可以根据通知执行某种操作。5.3.1创建事件创建并使用事件的步骤：l 为事件建立代表l 创建一个类来给事件处理程序传递参数、l 声明事件对应的代码l 创建事件发生时将执行的代码。1、 事件的代表要使用事件，首先为事件创建一个代表。创建格式为：Delegat

8、e void EventHandlerName(object source, xxxEventArgs e);EventHandlerName 事件代表名称。事件的代表总是两个参数，第一个是引发事件的源，第二个参数是一个可包含事件处理程序可以使用的数据。例：Delegate void CharEventHandler(object source, CharEventArgs e);2、 EventArgs 类EventArgs类用于将数据传递给事件处理程序，它可以派生出一些新类，即包含用于存储所需值的数据成员。派生类格式：Public class xxxEventArgs:EventArgs/

9、数据成员Public xxxEventArgs(type name) 初始化数据成员假如创建的代表名为CharEventHandler，它传递一个CharEventArgs对象。代码：Public class CharEventArgs：EventArgs Public char currchar； Public CharEventArgs（char Currchar） This.Currchar=Currchar; 3、 事件类的代码创建一个引发事件的类，包含事件的声明。事件声明格式：Public event xxxEventHandler Eventname;xxxEventHandler

10、 /事件代表、Eventname 事件实例。例：Class CharChecker Char curr_char; Public event CharEventHandler TestChar; /创建能委托给代表的事件对象 Public char curr_char Get Return curr_char;Set If (TestChar!=null) CharEventArgs args=new CharEventArgs(value); TestChar(this,args); /调用事件代表 Curr_char=args.CurrChar; 4、 创建事件处理程序事件处理程序在事件发

11、生时被通知，事件处理程序是使用代表的格式创建的一个方法。格式：Void handlername（object source,xxxEventArgs argName） /处理代码。例：static void Drop_A(object scource,CharEventArgs e) If(e.CurrChar=a| e.CurrChar=A) Console.WriteLine(“aaaaaaaa”); e.CurrChar=X; 5、 将事件处理程序和事件关联起来要将事件处理程序和事件关联起来，必须首先声明一个包含事件的对象。例：CharChecker tester=new CharChe

12、cker();要将事件处理程序和事件关联起来使用+=运算符。格式为：oibjectWithEventName.EventObj +=new EventDelegateName(EventName);oibjectWithEventName /事件类声明的对象+= /表示指示器例：Tester.TestChar +=new CharEventHandler(Drop_A);6、 实例：using System;delegate void CharEventHandler(object source, CharEventArgs e); /定义代表public class CharEventArg

13、s : EventArgs /定义传递事件类 public char CurrChar; public CharEventArgs(char CurrChar) this.CurrChar = CurrChar; class CharChecker char curr_char; public event CharEventHandler TestChar; /创建事件实例 public char Curr_Char get return curr_char; set if (TestChar != null ) CharEventArgs args = new CharEventArgs(v

14、alue); TestChar(this, args); curr_char = args.CurrChar; class myApp static void Main() CharChecker tester = new CharChecker(); tester.TestChar += new CharEventHandler(Drop_A); tester.Curr_Char = B; Console.WriteLine(0, tester.Curr_Char); tester.Curr_Char = r; Console.WriteLine(0, tester.Curr_Char);

15、tester.Curr_Char = a; Console.WriteLine(0, tester.Curr_Char); tester.Curr_Char = d; Console.WriteLine(0, tester.Curr_Char); static void Drop_A(object source, CharEventArgs e) if(e.CurrChar = a | e.CurrChar = A ) Console.WriteLine(Dont like a!); e.CurrChar = X; 7、多个事件处理程序using System;delegate void Ch

16、arEventHandler(object source, CharEventArgs e);public class CharEventArgs : EventArgs public char CurrChar; public CharEventArgs(char CurrChar) this.CurrChar = CurrChar; class CharChecker char curr_char; public event CharEventHandler TestChar; public char Curr_Char get return curr_char; set if (Test

17、Char != null ) CharEventArgs args = new CharEventArgs(value); TestChar(this, args); curr_char = args.CurrChar; class MyApp static void Main() CharChecker tester = new CharChecker(); tester.TestChar += new CharEventHandler(Drop_A); tester.TestChar += new CharEventHandler(Change_D); tester.Curr_Char =

18、 B; Console.WriteLine(0, tester.Curr_Char); tester.Curr_Char = r; Console.WriteLine(0, tester.Curr_Char); tester.Curr_Char = a; Console.WriteLine(0, tester.Curr_Char); tester.Curr_Char = d; Console.WriteLine(0, tester.Curr_Char); static void Drop_A(object source, CharEventArgs e) if(e.CurrChar = a |

19、 e.CurrChar = A ) Console.WriteLine(Dont like a!); e.CurrChar = X; / new event handler. static void Change_D(object source, CharEventArgs e) if(e.CurrChar = d | e.CurrChar = D ) Console.WriteLine(Ds are good!); e.CurrChar = Z; 7、 删除事件处理程序using System;delegate void CharEventHandler(object source, Cha

20、rEventArgs e);public class CharEventArgs : EventArgs public char CurrChar; public CharEventArgs(char CurrChar) this.CurrChar = CurrChar; class CharChecker char curr_char; public event CharEventHandler TestChar; public char Curr_Char get return curr_char; set if (TestChar != null ) CharEventArgs args

21、 = new CharEventArgs(value); TestChar(this, args); curr_char = args.CurrChar; class MyApp static void Main() CharChecker tester = new CharChecker(); tester.TestChar += new CharEventHandler(Drop_A); tester.TestChar += new CharEventHandler(Change_D); tester.Curr_Char = B; Console.WriteLine(0, tester.C

22、urr_Char); tester.Curr_Char = r; Console.WriteLine(0, tester.Curr_Char); tester.Curr_Char = a; Console.WriteLine(0, tester.Curr_Char); tester.Curr_Char = d; Console.WriteLine(0, tester.Curr_Char); / Remove event handler. Console.WriteLine(nRemoving event handler.); tester.TestChar -= new CharEventHa

23、ndler(Change_D); / Try D-a-d. tester.Curr_Char = D; Console.WriteLine(0, tester.Curr_Char); tester.Curr_Char = a; Console.WriteLine(0, tester.Curr_Char); tester.Curr_Char = d; Console.WriteLine(0, tester.Curr_Char); static void Drop_A(object source, CharEventArgs e) if(e.CurrChar = a | e.CurrChar =

24、A ) Console.WriteLine(Dont like a!); e.CurrChar = X; / new event handler. static void Change_D(object source, CharEventArgs e) if(e.CurrChar = d | e.CurrChar = D ) Console.WriteLine(Ds are good!); e.CurrChar = Z; public delegate void EventHandler(object sender, EventArgs e);public class Button: Cont

25、rolpublic event EventHandler Click;protected void OnClick(EventArgs e) if (Click != null) Click(this, e);public void Reset() Click = null;5.4 事件的预订和撤消两个按钮 OK 和 Cancel 按钮程序清单 public class LoginDialog: FormButton OkButton;Button CancelButton;public LoginDialog() OkButton = new Button(.);OkButton.Click

26、 += new EventHandler(OkButtonClick);CancelButton = new Button(.);CancelButton.Click += new EventHandler(CancelButtonClick);void OkButtonClick(object sender, EventArgs e) / 处理 OkButton.Click 事件void CancelButtonClick(object sender, EventArgs e) / 处理 CancelButton.Click 事件使用了 Button 类的两个实例 ，事件的预订是通过为事件加上左操作符+= 来实现的OkButton.Click += new EventHandler(OkButtonClick);这样 只要事件被触发 方法就会被调用事件的撤消则采用左操作符 -=OkButton.Click -= new EventHandler(OkButtonClick);5.5 事件访问器添加访问器声明 add-accessor-declaration和删除访问器声明 remove-accessor-declarationclass Control: Component/ Unique keys for eventss