Here is my solution along with the screenshot = yellow means the static rows which are only printed - the other rows are dynamic and can be solved with for loop and some thinking! :-) Cheers

here is the solution itself:
using System;
class SandGlass
{
static void Main(string[] args)
{
int n = int.Parse(Console.ReadLine());
Console.WriteLine("{0}",
new string(('*'), n));
for (int i = 0; i < n / 2 - 1; i++)
{
Console.WriteLine("{0}{1}{0}",
new string(('.'), i + 1),
new string(('*'), n - 2 - 2 * i));
}
Console.WriteLine("{0}*{0}",
new string(('.'), n / 2));
for (int i = 0; i < n / 2 - 1; i++)
{
Console.WriteLine("{0}{1}{0}",
new string(('.'), n / 2 - 1 - i),
new string(('*'), 3 + i * 2));
}
Console.WriteLine("{0}",
new string(('*'), n));
}
}