异常(Exception)

  1、IOException

public static void Test1()
        {
            FileStream fs = null;
            try
            {
                fs = new FileStream("d:\file.txt", FileMode.Open);
                fs.ReadByte();
                Console.WriteLine("OK");
            }
            catch (IOException)
            {
                Console.WriteLine("IOException");
            }
            catch
            {
                Console.WriteLine("ELSE Exception");
            }
            finally
            {
                if (fs != null)
                {
                    fs.Close();
                    fs = null;
                }
            }
        }

  2、FileNotFoundException 继承自 IOException

        public static void Test1()
        {
            FileStream fs = null;
            try
            {
                fs = new FileStream("d:\file.txt", FileMode.Open);
                fs.ReadByte();
                Console.WriteLine("OK");
            }
            catch (FileNotFoundException)
            {
                Console.WriteLine("FileNotFoundException");
            }
            catch (IOException)
            {
                Console.WriteLine("IOException");
            }
            finally
            {
                if (fs != null)
                {
                    fs.Close();
                    fs = null;
                }
            }
        }

  3、NullReferenceException

        /// <summary>
        /// 委托
        /// </summary>
        /// <param name="str">委托参数</param>
        public delegate void Show(string str);

        /// <summary>
        /// 事件
        /// </summary>
        public static event Show ShowEvent;

        public static void Test2()
        {
            try
            {
                Console.WriteLine(ShowEvent.GetInvocationList().Count());
            }
            catch (NullReferenceException)
            {
                Console.WriteLine("NullReferenceException");
            }
        }