8.6 try语句

可以通过 MSDN 查方法相应的异常。
如 Int32.Parse 方法 (String) 就有以下异常。

粗略的处理异常：

        static void Main(string[] args)
        {
            Calculator c = new Calculator();
            Console.WriteLine(c.Add("abc","100"));
        }
    }
    class Calculator
    {
        public int Add(string arg1,string arg2)
        {
            int a = 0;
            int b = 0;
            try
            {
                a = int.Parse(arg1);
                b = int.Parse(arg2);
            }
            catch
            {
                Console.WriteLine("Your argument(s) have error!");
            }
            int result = a + b;
            return result;
        }
    }

精确的处理异常：

    class Program
    {
        static void Main(string[] args)
        {
            Calculator c = new Calculator();
            Console.WriteLine(c.Add(null,"100"));
        }
    }
    class Calculator
    {
        public int Add(string arg1,string arg2)
        {
            int a = 0;
            int b = 0;
            try
            {
                a = int.Parse(arg1);
                b = int.Parse(arg2);
            }
            catch(ArgumentNullException)
            {
                Console.WriteLine("Your argument(s) are null.");
            }
            catch(FormatException)
            {
                Console.WriteLine("Your argument(s) are not number.");
            }
            catch (OverflowException)
            {
                Console.WriteLine("Out of rangle!");
            }
            int result = a + b;
            return result;
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            Calculator c = new Calculator();
            Console.WriteLine(c.Add("9999999999999999999999999999","100"));
        }
    }
    class Calculator
    {
        public int Add(string arg1,string arg2)
        {
            int a = 0;
            int b = 0;
            try
            {
                a = int.Parse(arg1);
                b = int.Parse(arg2);
            }
            catch(ArgumentNullException ane)
            {
                Console.WriteLine(ane.Message);
            }
            catch(FormatException fe)
            {
                Console.WriteLine(fe.Message);
            }
            catch (OverflowException oe)
            {
                Console.WriteLine(oe.Message);
            }
            int result = a + b;
            return result;
        }
    }

finally

• 应该把释放系统资源的语句写在 finally block 里面

• 有时候也在 finally block 里面写 log

    class Program
    {
        static void Main(string[] args)
        {
            Calculator c = new Calculator();
            Console.WriteLine(c.Add("abc","100"));
        }
    }
    class Calculator
    {
        public int Add(string arg1,string arg2)
        {
            int a = 0;
            int b = 0;
            bool hasError = false;
            try
            {
                a = int.Parse(arg1);
                b = int.Parse(arg2);
            }
            catch(ArgumentNullException ane)
            {
                Console.WriteLine(ane.Message);
                hasError = true;
            }
            catch(FormatException fe)
            {
                Console.WriteLine(fe.Message);
                hasError = true;
            }
            catch (OverflowException oe)
            {
                Console.WriteLine(oe.Message);
                hasError = true;
            }
            finally
            {
                if (hasError)
                {
                    Console.WriteLine("Execution has error!");
                }
                else
                {
                    Console.WriteLine("Done!");
                }
            }
            int result = a + b;
            return result;
        }
    }

throw

throw 将异常抛给调用者。
throw 关键字的语法比较灵活。

    class Program
    {
        static void Main(string[] args)
        {
            Calculator c = new Calculator();
            int r = 0;
            try
            {
                r = c.Add("999999999999999999999", "100");
            }
            catch (OverflowException oe)
            {
                Console.WriteLine(oe.Message);
            }
        }
    }
    class Calculator
    {
        public int Add(string arg1,string arg2)
        {
            int a = 0;
            int b = 0;
            try
            {
                a = int.Parse(arg1);
                b = int.Parse(arg2);
            }
            catch(ArgumentNullException ane)
            {
                Console.WriteLine(ane.Message);
            }
            catch(FormatException fe)
            {
                Console.WriteLine(fe.Message);
            }
            catch (OverflowException oe)
            {
                //Console.WriteLine(oe.Message);
                throw oe;
            }
            int result = a + b;
            return result;
        }
    }