C#錯誤和異常處理典型例子

檢查使用者輸入的是否是一個0-5中間的數字： 多重catch塊

 

using System;using System.Collections.Generic;using System.Linq;using System.Text;namespace ExceptionDemo{    class Program    {        static void Main(string[] args)        {            string userInput;            while (true)            {                try                {                    Console.Write("Input a number between 0 and 5" + "(or just hit return to exist)>");                    userInput = Console.ReadLine();                    if (userInput == "")                        break;                    int index = Convert.ToInt32(userInput);                    if (index < 0 || index > 5)                        throw new IndexOutOfRangeException("You typed in  " + userInput);                    Console.WriteLine("Your number was " + index);                }                catch (IndexOutOfRangeException ex)                {                    Console.WriteLine("Exception: " + "Number should between 0 and 5." + ex.Message);                }                catch (Exception ex)                {                    Console.WriteLine("An exception was thrown. Message was: {0}" + ex.Message);                }                catch                {                    Console.WriteLine("Some other exception has occured");                }                finally                {                    Console.WriteLine("Thank you");                }            }        }    }}

當輸入的是非0-5之間的數位時候，拋出的第一個異常，如果是一個字串，拋出的第二個異常。第三個異常不帶參數，這個catch塊處理的是其他沒有用C#編程的代碼。

 

下面這個是MSDN一個try…finally的異常處理

static void CodeWithCleanup()        {            System.IO.FileStream file = null;            System.IO.FileInfo fileInfo = null;            try            {                fileInfo = new System.IO.FileInfo("C:\\file.txt");                file = fileInfo.OpenWrite();                file.WriteByte(0xF);            }            catch (System.Exception e)            {                System.Console.WriteLine(e.Message);            }            finally            {                if (file != null)                {                    file.Close();                }            }        }