namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            string a = "**";
           
            for (int i = 0; i < 3; i++)//(有多少行）
            {
               
                for (int j = 0; j < 3; j++)//（每行有多少个）(n*a+a)

                    Console.Write(a);
                Console.WriteLine(a);
            }
            Thread.Sleep (5000);

C#代码