C#语言基础（二）

[align=left]流程控制[/align]
8、if….else语句
[align=left]using System;[/align]
[align=left]using System.Collections.Generic;[/align]
[align=left]using System.Text;[/align]
[align=left]//if...else选择语句[/align]
[align=left]namespace IfElseTest[/align]
[align=left]{[/align]
[align=left] class IfElseTest[/align]
[align=left] {[/align]
[align=left] static void Main(string[] args)[/align]
[align=left] {[/align]
[align=left] bool flagCheck = true;[/align]
[align=left] if (flagCheck == true)[/align]
[align=left] {[/align]
[align=left] Console.WriteLine("The flag is set to true.");[/align]
[align=left] }[/align]
[align=left] else[/align]
[align=left] {[/align]
[align=left] Console.WriteLine("The flag is set to false.");[/align]
[align=left] }[/align]
[align=left] }[/align]
[align=left] }[/align]
[align=left]}[/align]
9、switch语句
[align=left]using System;[/align]
[align=left]using System.Collections.Generic;[/align]
[align=left]using System.Text;[/align]
[align=left]//switch语句[/align]
[align=left]namespace SwitchTest[/align]
[align=left]{[/align]
[align=left] class SwitchTest[/align]
[align=left] {[/align]
[align=left] static void Main(string[] args)[/align]
[align=left] {[/align]
[align=left] int caseSwitch = 1;[/align]
[align=left] switch (caseSwitch)[/align]
[align=left] {[/align]
[align=left] case 1:[/align]
[align=left] Console.WriteLine("Case 1");[/align]
[align=left] break;[/align]
[align=left] case 2:[/align]
[align=left] Console.WriteLine("Case 2");[/align]
[align=left] break;[/align]
[align=left] default:[/align]
[align=left] Console.WriteLine("Default case");[/align]
[align=left] break;[/align]
[align=left] }[/align]
[align=left] }[/align]
[align=left] }[/align]
[align=left]}[/align]
10、for循环语句
[align=left]using System;[/align]
[align=left]using System.Collections.Generic;[/align]
[align=left]using System.Text;[/align]
[align=left]//for循环语句[/align]
[align=left]namespace ForLoopTest[/align]
[align=left]{[/align]
[align=left] class ForLoopTest[/align]
[align=left] {[/align]
[align=left] static void Main(string[] args)[/align]
[align=left] {[/align]
[align=left] for (int i = 1; i <= 5; i++)[/align]
[align=left] {[/align]
[align=left] Console.WriteLine(i);[/align]
[align=left] }[/align]
[align=left] }[/align]
[align=left] }[/align]
[align=left]}[/align]
11、while循环语句
[align=left]using System;[/align]
[align=left]using System.Collections.Generic;[/align]
[align=left]using System.Text;[/align]
[align=left]//while循环语句[/align]
[align=left]namespace WhileText[/align]
[align=left]{[/align]
[align=left] class WhileTest[/align]
[align=left] {[/align]
[align=left] static void Main(string[] args)[/align]
[align=left] {[/align]
[align=left] int n = 1;[/align]
[align=left] while (n < 6)[/align]
[align=left] {[/align]
[align=left] Console.WriteLine("Current value of n is {0}", n);[/align]
[align=left] n++;[/align]
[align=left] }[/align]
[align=left] }[/align]
[align=left] }[/align]
[align=left]}[/align]
12、do…while循环语句
[align=left]using System;[/align]
[align=left]using System.Collections.Generic;[/align]
[align=left]using System.Text;[/align]
[align=left]//do...while循环语句[/align]
[align=left]namespace TestDoWhile[/align]
[align=left]{[/align]
[align=left] class TestDoWhile[/align]
[align=left] {[/align]
[align=left] static void Main(string[] args)[/align]
[align=left] {[/align]
[align=left] int x = 0;[/align]
[align=left] do[/align]
[align=left] {[/align]
[align=left] Console.WriteLine(x);[/align]
[align=left] x++;[/align]
[align=left] }[/align]
[align=left] while (x < 5);[/align]
[align=left] }[/align]
[align=left] }[/align]
[align=left]}[/align]
13、foreach语句
[align=left]using System;[/align]
[align=left]using System.Collections.Generic;[/align]
[align=left]using System.Text;[/align]
[align=left]//foreach语句[/align]
[align=left]namespace ForeachTest[/align]
[align=left]{[/align]
[align=left] class ForeachTest[/align]
[align=left] {[/align]
[align=left] static void Main(string[] args)[/align]
[align=left] {[/align]
[align=left] int[] fibarray = new int[] { 0, 1, 2, 3, 5, 8, 13 };[/align]
[align=left] foreach (int i in fibarray)[/align]
[align=left] {[/align]
[align=left] Console.WriteLine(i);[/align]
[align=left] }[/align]
[align=left] }[/align]
[align=left] }[/align]
[align=left]}[/align]
14、throw语句
[align=left]using System;[/align]
[align=left]using System.Collections.Generic;[/align]
[align=left]using System.Text;[/align]
[align=left]//throw语句[/align]
[align=left]namespace ThrowTest[/align]
[align=left]{[/align]
[align=left] class ThrowTest[/align]
[align=left] {[/align]
[align=left] static void Main(string[] args)[/align]
[align=left] {[/align]
[align=left] string s = null;[/align]
[align=left] if (s == null)[/align]
[align=left] {[/align]
[align=left] throw new ArgumentNullException();[/align]
[align=left] }[/align]
[align=left] Console.Write("The string is null.");[/align]
[align=left] }[/align]
[align=left] }[/align]
[align=left]}[/align]
15、try…catch语句
[align=left]using System;[/align]
[align=left]using System.Collections.Generic;[/align]
[align=left]using System.Text;[/align]
[align=left]//try...catch语句,try块包含对可能导致异常的MyMethod()方法的调用。[/align]
[align=left]//catch子句包含仅在屏幕上显示消息的异常处理程序。[/align]
[align=left]//当从MyMethod()内部调用throw语句时，系统查找catch语句并显示Exception caught消息。[/align]
[align=left]namespace TrycatchTest[/align]
[align=left]{[/align]
[align=left] class TrycatchTest[/align]
[align=left] {[/align]
[align=left] static void Main(string[] args)[/align]
[align=left] {[/align]
[align=left] try[/align]
[align=left] {[/align]
[align=left] string s = null;[/align]
[align=left] ProcessString(s);[/align]
[align=left] }[/align]
[align=left] catch (Exception e)[/align]
[align=left] {[/align]
[align=left] Console.WriteLine("{0} Exception caught.", e);[/align]
[align=left] }[/align]
[align=left] }[/align]
[align=left] static void ProcessString(string s)[/align]
[align=left] {[/align]
[align=left] if (s == null)[/align]
[align=left] {[/align]
[align=left] throw new ArgumentNullException();[/align]
[align=left] }[/align]
[align=left] }[/align]
[align=left] }[/align]
[align=left]}[/align]
16、try…finally语句
[align=left]using System;[/align]
[align=left]using System.Collections.Generic;[/align]
[align=left]using System.Text;[/align]
[align=left]//try...finally语句，代码中有一个导致异常的无效转换语句，当程序运行时，将产生一条运行时错误信息，[/align]
[align=left]//但程序没有去处理异常信息，而是控制传递给finally子句继续执行并显示输出。[/align]
[align=left]namespace TryFinallyTest[/align]
[align=left]{[/align]
[align=left] class TryFinallyTest[/align]
[align=left] {[/align]
[align=left] static void Main(string[] args)[/align]
[align=left] {[/align]
[align=left] int i = 123;[/align]
[align=left] string s = "Some string";[/align]
[align=left] object o = s;[/align]
[align=left] try[/align]
[align=left] {[/align]
[align=left] i = (int)o;//包含一个字符串，无法转换为int类型[/align]
[align=left] }[/align]
[align=left] finally[/align]
[align=left] {[/align]
[align=left] Console.Write("i={0}", i);[/align]
[align=left] }[/align]
[align=left] }[/align]
[align=left] }[/align]
[align=left]}[/align]
17、try…catch…finally语句
[align=left]using System;[/align]
[align=left]using System.Collections.Generic;[/align]
[align=left]using System.Text;[/align]
[align=left]//try...catch...finally语句，代码演示了捕捉异常，并作出相应处理。[/align]
[align=left]namespace TryCatchFinallyTest[/align]
[align=left]{[/align]
[align=left] class TryCatchFinallyTest[/align]
[align=left] {[/align]
[align=left] static void Main(string[] args)[/align]
[align=left] {[/align]
[align=left] try[/align]
[align=left] {[/align]
[align=left] Console.WriteLine("Executing the try statement.");[/align]
[align=left] throw new NullReferenceException();[/align]
[align=left] }[/align]
[align=left] catch (NullReferenceException e)[/align]
[align=left] {[/align]
[align=left] Console.WriteLine("{0} Caught exception #1.", e);[/align]
[align=left] }[/align]
[align=left] catch[/align]
[align=left] {[/align]
[align=left] Console.WriteLine("Caught exception #2.");[/align]
[align=left] }[/align]
[align=left] finally[/align]
[align=left] {[/align]
[align=left] Console.WriteLine("Executing finally block.");[/align]
[align=left] }[/align]
[align=left] }[/align]
[align=left] }[/align]
[align=left]}[/align]