public IEnumerable<int> AllPalindromes()
{
string highestNumberString = string.Empty;
for (int i = 0; i < _numberOfDigits; i++)
{
highestNumberString += "9";
}
int highestNumber = Convert.ToInt32(highestNumberString);
for (int outer = highestNumber; outer > 0 ; outer--)
{
for (int inner = highestNumber; inner > 0 ; inner--)
{
var value = outer*inner;
if (value % 11 == 0 && IsPalindrome(value.ToString()))
yield return value;
}
}
}