计算1-2+3-4+…+99-100的结果。
            static void Main(string[] args)         
            {            
                int i,  n = 100, flag = 1,sum=0;            
                for (i = 1; i<=100; i++)              
                {                 
                    sum += flag*i;               
                    flag = flag*(-1);            
                }            
                Console.WriteLine("1-2+3-4+…+99-100的结果为：" + sum);            
                Console.Read();         
            }  
九九乘法表

            static void Main(string[] args)         
            {            
                int i, j;            
                for (i = 1; i <= 9; i++)            
                {                 
                    for (j = 1; j<=9; j++)               
                    {                    
                        Console.Write("{0}*{1}={2}\t", j, i, i*j);               
                    }                 
                    Console.WriteLine();                              
                }            
                Console.Read();         
            }