Write a method to process the path:
private bool IsThisMonth(DateTime now, string path)
{
DateTime dt;
if (!DateTime.TryParseExact(Path.GetExtension(path),
".yyyy-MM-dd",
CultureInfo.InvariantCulture,
DateTimeStyles.None,
out dt))
{
return false;
}
return dt.Year == now.Year && dt.Month == now.Month;
}
Then it's trivial:
DateTime now = DateTime.Now;
string[] thisMonth = inputFilePaths.Where(f => IsThisMonth(now, f)).ToArray();