Reboot computer in C# / .NET

By Robert Ellison. Updated on Monday, May 2, 2022.

.NET doesn’t support rebooting, logging off or shutting down your computer though a managed API. Searching for the best way to do this brings up three options: WMI, shutdown.exe and ExitWindowsEx.

I regard WMI as the last resort of the desperate. Weakly typed magic string juju.

Calling Process.Start(“shutdown.exe /r /t 0”) might work, but how would you know? And you’ve got the overheard of starting a new process just to accomplish a reboot. Lazy.

The best way to reboot is P/Invoke to ExitWindowsEx. Unfortunately there’s some really awful sample code out there which will either fail to do anything or mask any errors. I’ve included a drop-in class below that fixes these problems.

If you read all the way through the documentation for ExitWindowsEx you’ll find this:

To shut down or restart the system, the calling process must use the AdjustTokenPrivileges function to enable the SE_SHUTDOWN_NAME privilege. For more information, see Running with Special Privileges.

So just calling ExitWindowsEx won’t do anything. The sample code below adjusts the process token and then reboots (change the flags passed to ExitWindowsEx to shutdown instead, or to pass in a different reason). You’ll also get a Win32Exception if a failure occurs. Catch this, and you can tell the user that they need to reboot manually.

static class NativeMethods { /// /// Reboot the computer /// public static void Reboot() { IntPtr tokenHandle = IntPtr.Zero; try { // get process token if (!OpenProcessToken(Process.GetCurrentProcess().Handle, TOKEN_QUERY | TOKEN_ADJUST_PRIVILEGES, out tokenHandle)) { throw new Win32Exception(Marshal.GetLastWin32Error(), "Failed to open process token handle"); } // lookup the shutdown privilege TOKEN_PRIVILEGES tokenPrivs = new TOKEN_PRIVILEGES(); tokenPrivs.PrivilegeCount = 1; tokenPrivs.Privileges = new LUID_AND_ATTRIBUTES[1]; tokenPrivs.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED; if (!LookupPrivilegeValue(null, SE_SHUTDOWN_NAME, out tokenPrivs.Privileges[0].Luid)) { throw new Win32Exception(Marshal.GetLastWin32Error(), "Failed to open lookup shutdown privilege"); } // add the shutdown privilege to the process token if (!AdjustTokenPrivileges(tokenHandle, false, ref tokenPrivs, 0, IntPtr.Zero, IntPtr.Zero)) { throw new Win32Exception(Marshal.GetLastWin32Error(), "Failed to adjust process token privileges"); } // reboot if (!ExitWindowsEx(ExitWindows.Reboot, ShutdownReason.MajorApplication | ShutdownReason.MinorInstallation | ShutdownReason.FlagPlanned)) { throw new Win32Exception(Marshal.GetLastWin32Error(), "Failed to reboot system"); } } finally { // close the process token if (tokenHandle != IntPtr.Zero) { CloseHandle(tokenHandle); } } } // everything from here on is from pinvoke.net [Flags] private enum ExitWindows : uint { // ONE of the following five: LogOff = 0x00, ShutDown = 0x01, Reboot = 0x02, PowerOff = 0x08, RestartApps = 0x40, // plus AT MOST ONE of the following two: Force = 0x04, ForceIfHung = 0x10, } [Flags] private enum ShutdownReason : uint { MajorApplication = 0x00040000, MajorHardware = 0x00010000, MajorLegacyApi = 0x00070000, MajorOperatingSystem = 0x00020000, MajorOther = 0x00000000, MajorPower = 0x00060000, MajorSoftware = 0x00030000, MajorSystem = 0x00050000, MinorBlueScreen = 0x0000000F, MinorCordUnplugged = 0x0000000b, MinorDisk = 0x00000007, MinorEnvironment = 0x0000000c, MinorHardwareDriver = 0x0000000d, MinorHotfix = 0x00000011, MinorHung = 0x00000005, MinorInstallation = 0x00000002, MinorMaintenance = 0x00000001, MinorMMC = 0x00000019, MinorNetworkConnectivity = 0x00000014, MinorNetworkCard = 0x00000009, MinorOther = 0x00000000, MinorOtherDriver = 0x0000000e, MinorPowerSupply = 0x0000000a, MinorProcessor = 0x00000008, MinorReconfig = 0x00000004, MinorSecurity = 0x00000013, MinorSecurityFix = 0x00000012, MinorSecurityFixUninstall = 0x00000018, MinorServicePack = 0x00000010, MinorServicePackUninstall = 0x00000016, MinorTermSrv = 0x00000020, MinorUnstable = 0x00000006, MinorUpgrade = 0x00000003, MinorWMI = 0x00000015, FlagUserDefined = 0x40000000, FlagPlanned = 0x80000000 } [StructLayout(LayoutKind.Sequential)] private struct LUID { public uint LowPart; public int HighPart; } [StructLayout(LayoutKind.Sequential)] private struct LUID_AND_ATTRIBUTES { public LUID Luid; public UInt32 Attributes; } private struct TOKEN_PRIVILEGES { public UInt32 PrivilegeCount; [MarshalAs(UnmanagedType.ByValArray, SizeConst = 1)] public LUID_AND_ATTRIBUTES[] Privileges; } private const UInt32 TOKEN_QUERY = 0x0008; private const UInt32 TOKEN_ADJUST_PRIVILEGES = 0x0020; private const UInt32 SE_PRIVILEGE_ENABLED = 0x00000002; private const string SE_SHUTDOWN_NAME = "SeShutdownPrivilege"; [DllImport("user32.dll", SetLastError = true)] [return: MarshalAs(UnmanagedType.Bool)] private static extern bool ExitWindowsEx(ExitWindows uFlags, ShutdownReason dwReason); [DllImport("advapi32.dll", SetLastError = true)] [return: MarshalAs(UnmanagedType.Bool)] private static extern bool OpenProcessToken(IntPtr ProcessHandle, UInt32 DesiredAccess, out IntPtr TokenHandle); [DllImport("advapi32.dll", SetLastError = true, CharSet=CharSet.Unicode)] [return: MarshalAs(UnmanagedType.Bool)] private static extern bool LookupPrivilegeValue(string lpSystemName, string lpName, out LUID lpLuid); [DllImport("kernel32.dll", SetLastError = true)] [return: MarshalAs(UnmanagedType.Bool)] private static extern bool CloseHandle(IntPtr hObject); [DllImport("advapi32.dll", SetLastError = true)] [return: MarshalAs(UnmanagedType.Bool)] private static extern bool AdjustTokenPrivileges(IntPtr TokenHandle, [MarshalAs(UnmanagedType.Bool)]bool DisableAllPrivileges, ref TOKEN_PRIVILEGES NewState, UInt32 Zero, IntPtr Null1, IntPtr Null2); }

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(Published to the Fediverse as: Reboot computer in C# / .NET #code #reboot #wmi #shutdown.exe #exitwindowsex #openprocesstoken #lookupprivilegevalue How to call ExitWindowsEx correctly to reboot a computer in C# / .NET including error handline in case you need to tell the user to reboot manually. )

code, reboot, wmi, shutdown.exe, exitwindowsex, openprocesstoken, lookupprivilegevalue

Comments

FYI, it looks like the embedded gist and its link get blocked by (some) corporate firewalls. I had to view on personal hardware.

∞ | by Dave on Monday, May 2 2022

Hi Massimo, there should be an embedded GIST in the post above. If that is failing to load for you then try here.

∞ | by Robert Ellison on Tuesday, December 14 2021

where is the code?

∞ | by Massimo on Tuesday, December 14 2021