Question

How to get the DateTime when the current process started?

Answer 1

The StartTime property on the Process type is returning that value:

Process.GetCurrentProcess().StartTime

This can of course be used to pick up the start time of other processes as well:

Process p = Process.GetProcessesByName("Notepad").FirstOrDefault();
if (p != null)
{
    Console.WriteLine(p.StartTime);
}