C# 定時無操做則退出登錄，回到登錄界面。

有時候根據需求須要爲程序添加在規定的時間內無操做則退出當前的登錄程序的功能，以下代碼模擬描述的需求功能。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace LockScreenMsg
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            label1.Height = 200;
        }

        [StructLayout(LayoutKind.Sequential)]
        struct LASTINPUTINFO
        {
            [MarshalAs(UnmanagedType.U4)]
            public int cbSize;
            [MarshalAs(UnmanagedType.U4)]
            public uint dwTime;
        }

        [DllImport("user32.dll")]
        static extern bool GetLastInputInfo(ref LASTINPUTINFO plii);

        static long GetLastInputTime()
        {
            LASTINPUTINFO vLastInputInfo = new LASTINPUTINFO();
            vLastInputInfo.cbSize = Marshal.SizeOf(vLastInputInfo);
            if (!GetLastInputInfo(ref vLastInputInfo))
            {
                return 0;
            }
            return Environment.TickCount - (long)vLastInputInfo.dwTime;
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            timer1.Enabled = true;
        }

        public string isNull = null;
        private void timer1_Tick(object sender, EventArgs e)
        {
           long time=GetLastInputTime()/1000;
            
            this.label1.Text = string.Format("用戶已經{0}秒沒有操做了", time);
           if (time >= 20)
           {
                this.Close();
           }
        }
    }
}