C#：如何唤醒已经关机的系统？

在框架中没有什么,所以你必须要“PInvoke”一点.
您需要调用的API是CreateWaitableTimer和SetWaitableTimer.
以下是一个完整的(Q& D)样本,说明如何设置
系统从sleep / hibernate唤醒使用上面的Win32 API.
请注意,这里我设置的相对唤醒时间为300000000 nSecs.
这意味着电脑会醒来(假设他睡着了或者睡着了)
设置定时器后30秒内休眠.
有关SetWaitableTimer及其参数的详细信息,请参阅MSDN文档.

using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace Willys
{
    class Program
    {
        [DllImport("kernel32.dll")]
        public static extern IntPtr CreateWaitableTimer(IntPtr lpTimerAttributes,bool bManualReset,string lpTimerName);

        [DllImport("kernel32.dll")]
        public static extern bool SetWaitableTimer(IntPtr hTimer,[In] ref long
        pDueTime,int lPeriod,IntPtr pfnCompletionRoutine,IntPtr
        lpArgToCompletionRoutine,bool fResume);

        [DllImport("kernel32",SetLastError = true,ExactSpelling = true)]
        public static extern Int32 WaitForSingleObject(IntPtr handle,uint
        milliseconds);

        static void Main()
        {
            SetWaitForWakeUpTime();
        }

        static IntPtr handle;
        static void SetWaitForWakeUpTime()
        {
            long duetime = -300000000; // negative value,so a RELATIVE due time
            Console.WriteLine("{0:x}",duetime);
            handle = CreateWaitableTimer(IntPtr.Zero,true,"MyWaitabletimer");
            SetWaitableTimer(handle,ref duetime,IntPtr.Zero,true);
            uint INFINITE = 0xFFFFFFFF;
            int ret = WaitForSingleObject(handle,INFINITE);
            MessageBox.Show("Wake up call");
        }
    }
}