Function that creates a timestamp in c#

I always use something like the following:

public static String GetTimestamp(this DateTime value)
{
    return value.ToString("yyyyMMddHHmmssfff");
}

This will give you a string like 200905211035131468, as the string goes from highest order bits of the timestamp to lowest order simple string sorting in your SQL queries can be used to order by date if you're sticking values in a database

I believe you can create a unix style datestamp accurate to a second using the following

//Find unix timestamp (seconds since 01/01/1970)
long ticks = DateTime.UtcNow.Ticks - DateTime.Parse("01/01/1970 00:00:00").Ticks;
ticks /= 10000000; //Convert windows ticks to seconds
timestamp = ticks.ToString();

Adjusting the denominator allows you to choose your level of precision

You could use the DateTime.Ticks property, which is a long and universal storable, always increasing and usable on the compact framework as well. Just make sure your code isn't used after December 31st 9999 ;)