How can I detect if a reboot is scheduled in the future after calling InitiateSystemShutdownW?

Question

I'm currently triggering a reboot using the windows api call InitiateSystemShutdownW. I'm passing this a dwTimeout value (10 minutes). I want to detect if this reboot (or any other reboot) has been scheduled:

[DllImport("advapi32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool InitiateSystemShutdownW([MarshalAs(UnmanagedType.LPWStr)]String lpMachineName, [MarshalAs(UnmanagedType.LPWStr)]String lpMessage, int dwTimeout, bool bForceAppsClosed, bool bRebootAfterShutdown);

I know that if I call it again I will receive an error message that tells me it's already scheduled (via GetLastWin32Error), but I need to do this without calling reboot again (because I may not want to actually trigger a reboot at this point).

I've tried calling GetSystemMetrics with the parameter SM_SHUTTINGDOWN but even though I know this is scheduled this returns false/0. I'm presuming this is an actual shutdown happening not scheduled to happen.

Is there anyway I can detect that this call is in progress or more generally whether a reboot is scheduled or not?

I'm calling these methods using C#/DllImport/interop so I need an api that is accessible from a c# process.

Answer 1

You can use the Windows Event Log API to access log entries on the "System" channel. That log records requests by a login to shutdown the system, and to abort a system shutdown.

This code shows how to use P/Invoke to get the number of system shutdown and shutdown abort requests within a specified timeframe before the query (in milliseconds). So if you have 2 scheduled shutdown requests in the last hour, and 1 abort request, then you have a pending shutdown in progress.

If you really want all of the details about a logged shutdown request, then you can use the EvtRender function to pull out the data in XML, and parse it. This code doesn't do that.

using System;
using System.Runtime.InteropServices;

namespace WindowsEventLogChecker
{
  // partial list from "winerror.h"
  public enum ERROR
  {
    ERROR_SUCCESS,
    ERROR_NO_MORE_ITEMS = 259,
    ERROR_EVT_CHANNEL_NOT_FOUND = 15007,
    ERROR_EVT_INVALID_QUERY = 15001
  }

  // this is our own enum
  public enum SystemEventType
  {
    Shutdown,
    Abort
  }

  // these are from "winevt.h"
  public enum EVT_QUERY_FLAGS
  {
    EvtQueryChannelPath = 0x1,
    EvtQueryFilePath = 0x2,
    EvtQueryForwardDirection = 0x100,
    EvtQueryReverseDirection = 0x200,
    EvtQueryTolerateQueryErrors = 0x1000
  }


  class Program
  {
    [DllImport("wevtapi.dll", EntryPoint = "EvtQuery", CallingConvention = CallingConvention.StdCall, SetLastError = true)]
    public static extern IntPtr EvtQuery(IntPtr session, [MarshalAs(UnmanagedType.LPWStr)] string path, [MarshalAs(UnmanagedType.LPWStr)] string query, int flags);

    [DllImport("wevtapi.dll", EntryPoint = "EvtNext", CallingConvention = CallingConvention.StdCall, SetLastError = true)]
    public static extern bool EvtNext(IntPtr resultSet, int batchSize, [MarshalAs(UnmanagedType.LPArray)] IntPtr[] eventBatch, int timeout, int flags, ref int nReturned);

    [DllImport("wevtapi.dll", EntryPoint = "EvtClose", CallingConvention = CallingConvention.StdCall)]
    public static extern bool EvtClose(IntPtr handle);

    [DllImport("kernel32.dll", EntryPoint = "GetLastError", CallingConvention = CallingConvention.StdCall)]
    public static extern int GetLastError();

    static void Main(string[] args)
    {
      // get the number of scheduled shutdowns in the last hour
      int nShutdowns = GetEventCount(SystemEventType.Shutdown, 3600000);

      // get the number of aborted shutdowns in the last hour
      int nAborts = GetEventCount(SystemEventType.Abort, 3600000);
    }

    private static int GetEventCount(SystemEventType evtType, int timeSpanMs)
    {
      ERROR status = ERROR.ERROR_SUCCESS;
      IntPtr hResult = IntPtr.Zero;
      IntPtr[] eventBatch = new IntPtr[10];

      // these 2 event id's, along with 'USER32' event source, denote requested
      // shutdown and abort, respectively
      string shutDownId = "1074";
      string abortId = "1075";

      // XPath query to get the event id, event source, and timespan in ms from now 
      // back to when the event was posted to the event log.
      string format = "*[System[(EventID = {0}) and Provider[@Name=\"USER32\"] and TimeCreated[timediff(@SystemTime) <= {1}]]]";

      // The "System" event channel
      string channelPath = "System";

      int nEvents = 0;
      int count = 0;
      string evtQuery;

      switch (evtType)
      {
        case SystemEventType.Shutdown:
        evtQuery = string.Format(format, shutDownId, timeSpanMs);
        break;
        case SystemEventType.Abort:
        evtQuery = string.Format(format, abortId, timeSpanMs);
        break;
        default:
        throw new InvalidOperationException();
      }
      hResult = EvtQuery(IntPtr.Zero, channelPath, evtQuery, (int)(EVT_QUERY_FLAGS.EvtQueryChannelPath | EVT_QUERY_FLAGS.EvtQueryReverseDirection));
      if (IntPtr.Zero == hResult)
      {
        status = (ERROR)GetLastError();

        if (status == ERROR.ERROR_EVT_CHANNEL_NOT_FOUND)
        {
          // log error
          return 0;
        }
        else if (status == ERROR.ERROR_EVT_INVALID_QUERY)
        {
          // log error
          return 0;
        }
        else
        {
          // log error
          return 0;
        }
      }
      while (EvtNext(hResult, 10, eventBatch, 1000, 0, ref nEvents))
      {
        for (int i = 0; i < nEvents; i++)
        {
          count++;
          if (eventBatch[i] != IntPtr.Zero)
          {
            EvtClose(eventBatch[i]);
          }
        }
      }
      status = (ERROR)GetLastError();
      if (status != ERROR.ERROR_NO_MORE_ITEMS)
      {
        // log error here and cleanup any remaining events
        for (int i = 0; i < nEvents; i++)
        {
          if (eventBatch[i] != IntPtr.Zero)
          {
            EvtClose(eventBatch[i]);
          }
        }
      }
      if (hResult != null)
      {
        EvtClose(hResult);
      }
      return count;
    }
  }
}