C#中计算质数的算法

for (int i = 2; i <= 100; i++)             {                 bool flag = true;                 int k =  Convert.ToInt32(Math.Sqrt(i));                 for (int j = 2; j <= k; j++)                 {                     if (i % j == 0)                     {                         flag = false;                                            break;                     }                 }                 if (flag == true)                 {                     Console.WriteLine(i);                 }             }             Console.ReadLine();