SatndbyResetter.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.Diagnostics;
using System.Threading;
using System.Runtime.InteropServices;

namespace StandbyResetter
{
    class Program
    {
        static void Main(string[] args)
        {
            var cpu_user = new PerformanceCounter("Processor", "% User Time", "_Total");

            float cpu;

            do
            {
                cpu = cpu_user.NextValue();
                Console.WriteLine("CPU:{0}", cpu);
                if (cpu > 20)
                   SetThreadExecutionState(ExecutionState.SystemRequired);
                Thread.Sleep(1000);

            } while (true);
        }
        [DllImport("kernel32.dll")]
        extern static ExecutionState SetThreadExecutionState(ExecutionState esFlags);
    }
    [FlagsAttribute]
    public enum ExecutionState : uint
    {
        // 関数が失敗した時の戻り値
        Null = 0,
        // スタンバイを抑止
        SystemRequired = 1,
        // 画面OFFを抑止
        DisplayRequired = 2,
        // 効果を永続させる。ほかオプションと併用する。
        Continuous = 0x80000000,
    }
}