c#实现系统休眠

class SystemSleepManagement
   {
       //定义API函数
       [DllImport("kernel32.dll")]
       static extern uint SetThreadExecutionState(ExecutionFlag flags);

       [Flags]
       enum ExecutionFlag : uint
       {
           System = 0x00000001,
           Display = 0x00000002,
           Continus = 0x80000000,
       }

       /// <summary>
       ///阻止系统休眠，直到线程结束恢复休眠
       /// </summary>
       /// <param name="includeDisplay">是否阻止关闭显示器</param>
       public static void PreventSleep(bool includeDisplay = false)
       {
           if (includeDisplay)
               SetThreadExecutionState(ExecutionFlag.System | ExecutionFlag.Display | ExecutionFlag.Continus);
           else
               SetThreadExecutionState(ExecutionFlag.System | ExecutionFlag.Continus);
       }

       /// <summary>
       ///恢复系统休眠
       /// </summary>
       public static void ResotreSleep()
       {
           SetThreadExecutionState(ExecutionFlag.Continus);
       }

       /// <summary>
       ///重置系统休眠计时器
       /// </summary>
       /// <param name="includeDisplay">是否阻止关闭显示器</param>
       public static void ResetSleepTimer(bool includeDisplay = false)
       {
           if (includeDisplay)
               SetThreadExecutionState(ExecutionFlag.System | ExecutionFlag.Display);
           else
               SetThreadExecutionState(ExecutionFlag.System);
       }
   }

因此，要实现下载时阻止程序休眠，则有两种实现方式：

下载期间起计时器定期执行ResetSleepTimer函数
下载开始时执行PreventSleep函数，下载结束后执行ResotreSleep函数。
另外，和阻止系统休眠类似，有的程序还需要有阻止屏保功能。