as 和 强制转换的区别

    class Program
    {
        static void Main(string[] args)
        {
            Object o = new Object();
            Machine m = (Machine)o;

            if(m == null)
            {
                Console.WriteLine("m is null");
            }
        }
    }

    class Machine { }

    class Computer : Machine
    {
    

    }

由于o不是Machine类型,强制转换会报错 未经处理的异常:  System.InvalidCastException 

如果将Machine m = (Machine)o换成Machine m = o as Machine;那么m为null，不会报错