方法一：调用windows自带的shutdown.exe(缺点：会出现倒计时窗口)

System.Diagnostics.Process.Start("shutdown.exe", "-r -f -t 15");

shutdown参数含义：-r关闭并重启动此计算机；-f 强制运行的应用程序关闭而没有警告；-t 15 延时15shutdown.exe的详细用法:
shutdown [-i | -l | -s | -r | -a] [-f] [-m //computername] [-t xx] [-c "comment"] [-d up:xx:yy]
没有参数 显示此消息(与 ? 相同)
-i 显示 GUI 界面，必须是第一个选项
-l 注销(不能与选项 -m 一起使用)
-s 关闭此计算机
-r 关闭并重启动此计算机
-a 放弃系统关机
-m //computername 远程计算机关机/重启动/放弃
-t xx 设置关闭的超时为 xx 秒
-c "comment" 关闭注释(最大 127 个字符)
-f 强制运行的应用程序关闭而没有警告
-d [u][p]:xx:yy 关闭原因代码
u 是用户代码
p 是一个计划的关闭代码
xx 是一个主要原因代码(小于 256 的正整数)
yy 是一个次要原因代码(小于 65536 的正整数)

方法二：调用API

复制代码 代码如下:
private const int SE_PRIVILEGE_ENABLED = 0x00000002;
private const int TOKEN_QUERY = 0x00000008;
private const int TOKEN_ADJUST_PRIVILEGES = 0x00000020;
private const string SE_SHUTDOWN_NAME = "SeShutdownPrivilege";

[Flags]
public enum ExitWindows : uint
{
LogOff = 0x00, //注销
ShutDown = 0x01, //关机
Reboot = 0x02, //重启
Force = 0x04,
PowerOff = 0x08,
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, Pack = 1)]
private struct TokPriv1Luid
{
public int Count;
public long Luid;
public int Attr;
}

[DllImport("kernel32.dll", ExactSpelling = true)]
private static extern IntPtr GetCurrentProcess();

[DllImport("advapi32.dll", ExactSpelling = true, SetLastError = true)]
private static extern bool OpenProcessToken(IntPtr h, int acc, ref IntPtr phtok);

[DllImport("advapi32.dll", SetLastError = true)]
private static extern bool LookupPrivilegeValue(string host, string name, ref long pluid);

[DllImport("advapi32.dll", ExactSpelling = true, SetLastError = true)]
private static extern bool AdjustTokenPrivileges(IntPtr htok, bool disall, ref TokPriv1Luid newst, int len, IntPtr prev, IntPtr relen);

[DllImport("user32.dll")]
private static extern bool ExitWindowsEx(ExitWindows uFlags, ShutdownReason dwReason);

/// <summary>
/// 关机、重启、注销windows
/// </summary>
/// <param name="flag"></param>
public static void DoExitWindows(ExitWindows flag)
{
TokPriv1Luid tp;
IntPtr hproc = GetCurrentProcess();
IntPtr htok = IntPtr.Zero;
OpenProcessToken(hproc, TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY, ref htok);
tp.Count = 1;
tp.Luid = 0;
tp.Attr = SE_PRIVILEGE_ENABLED;
LookupPrivilegeValue(null, SE_SHUTDOWN_NAME, ref tp.Luid);
AdjustTokenPrivileges(htok, false, ref tp, 0, IntPtr.Zero, IntPtr.Zero);
ExitWindowsEx(flag, ShutdownReason.MajorOther);
}