How to know when was Windows started or shutdown?

Question

I need to develop a program in C# find out when was Windows started or shutdown.

Is there a log file that I can read to know Windows start and shutdown times? Or do

Answer 1

As Reed pointed out you could access the Event Logs and see when they were created. AFAIK there are no specific event entries for system startup/shutdown, but you could look for services that are usually started/stopped with Windows. Though using this approach means it won't be 100% accurate, say if it crashes or it's manually started/stopped/restarted. One event I consider is the most accurate is EventLog service start/stop event.

if (EventLog.Exists("System"))
{
    var log = new EventLog("System", Environment.MachineName, "EventLog");

    var entries = new EventLogEntry[log.Entries.Count];
    log.Entries.CopyTo(entries, 0);

    var startupTimes = entries.Where(x => x.InstanceId == 2147489653).Select(x => x.TimeGenerated);
    var shutdownTimes = entries.Where(x => x.InstanceId == 2147489654).Select(x => x.TimeGenerated);
}

Edit

Turns out there was a shutdown event. You can replace the Linq to get it:

var shutdownEvents = entries.Where(x => x.InstanceId == 2147484722);