int[,] a = { {1,2,3}, {4,5,6}, {7,8,9} };
for (int i = 0; i < a.GetLength(0); i++)
{
    for (int j=0; j < a.GetLength(1);j++)
    {
        Console.Write(a[i,j]);
    }
    Console.Write("\n");
}
int sum = 0;
for (int j = 0; j < a.GetLength(1); j++)
{
    sum += a[1, j];
}
int p = a[0, 0];
for (int i = 1; i < a.GetLength(0); i++)
{
    p *= a[i,0];
}
Console.WriteLine("Сумма = "+sum+"\nПроизведение = "+p);