for (int i = 10; i >= 1; i--)
{
for (int k = 1; k <= 10 - i; k++)
{
Console.Write(" ");
}

for (int j = 1; j <= i; j++)
{
Console.Write("* ");
}

Console.WriteLine();
}

for (int i = 1; i <= 10; i++)
{
for (int k = 1; k <= 10 - i; k++)
{
Console.Write(" ");
}

for (int j = 1; j <= i; j++)
{
Console.Write("* ");
}

Console.WriteLine();
}