热键注册类

using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;
  
namespace test
{
     /// <summary>
     /// 热键类
     /// </summary>
     public class HotKey
     {
         /// <summary>
         /// 如果函数执行成功，返回值不为0，如果执行失败，返回值为0
         /// </summary>
         /// <returns></returns>
         [DllImport("user32.dll", SetLastError = true)]
         public static extern bool RegisterHotKey(
             IntPtr hWnd,           // 窗口的句柄, 当热键按下时，会产生WM_HOTKEY信息，该信息该会发送该窗口句柄
             int id,                      // 定义热键ID,属于唯一标识热键的作用
             uint fsModifiers,            // 热键只有在按下Alt、 Ctrl、Shift、Windows等键时才会生效，即才会产生WM_HOTKEY信息
             Keys vk                   // 虚拟键,即按了Alt+Ctrl+ X ，X就是代表虚拟键
             );

        [DllImport("user32.dll", SetLastError = true)]
         public static extern bool UnregisterHotKey(
             IntPtr hWnd,                   // 窗口句柄
             int id                         // 要取消热键的ID
             );
     }
}　

测试方法：

public partial class Form1 : Form
         {

            [Flags]
             public enum KeyModifiers
             { //定义热键值字符串(热键值是系统规定的，不能改变)
                 None = 0,
                 Alt = 1,
                 Ctrl = 2,
                 Shift = 4,
                 WindowsKey = 8
             }

            public Form1()
             {
                 InitializeComponent();
             }

            //窗体加载时-注册快捷键
             private void Form1_Load(object sender, EventArgs e)
             {
                 uint ctrlHotKey = (uint)(KeyModifiers.Alt | KeyModifiers.Ctrl);
                 // 注册热键为Alt+Ctrl+A, "100"为唯一标识热键
                 HotKey.RegisterHotKey(Handle, 100, ctrlHotKey, Keys.A);
             }

            //截图按钮
             private void button1_Click(object sender, EventArgs e)
             {
                 if (this.WindowState != FormWindowState.Minimized)
                 {
                     this.WindowState = FormWindowState.Minimized;
                     Thread.Sleep(200);
                 }
                 int swidth = Screen.PrimaryScreen.Bounds.Width;
                 int sheight = Screen.PrimaryScreen.Bounds.Height;
                 Bitmap btm = new Bitmap(swidth, sheight); //空图与屏幕同大小
                 Graphics g = Graphics.FromImage(btm); //空图的画板
                 g.CopyFromScreen(new Point(0, 0), new Point(0, 0), new Size(swidth, sheight)); //将屏幕内容复制到空图
                 Cutter cutter = new Cutter(btm); //传送截图
                 cutter.FormBorderStyle = FormBorderStyle.None; //截图全屏，无边框
                 cutter.BackgroundImage = btm; //新的窗体截图做背景
                 cutter.Show();
             }
             private void tiaoZ(object sender, ElapsedEventArgs e)
             {
             }


             //窗体关闭-取消热键
             private void Form1_FormClosing(object sender, FormClosingEventArgs e)
             {
                 HotKey.UnregisterHotKey(Handle, 100);
             }

            //快捷键按下执行的事件
             private void GlobalKeyProcess()
             {
                 this.WindowState = FormWindowState.Minimized;
                 Thread.Sleep(200);
                 button1.PerformClick();
             }

            //重写。监视系统消息，调用对应方法
             protected override void WndProc(ref Message m)
             {
                 const int WM_HOTKEY = 0x0312;
                 //如果m.Msg的值为0x0312（我也不知道为什么是0x0312）那么表示用户按下了热键
                 switch (m.Msg)
                 {
                     case WM_HOTKEY:
                         if (m.WParam.ToString().Equals("100"))
                         {
                             GlobalKeyProcess();
                         }
                         //todo  其它热键
                         break;
                 }
                 // 将系统消息传递自父类的WndProc
                 base.WndProc(ref m);
             }
         }

=================

在网上查资料，觉得可能有用。没有实测测试，留着以后使用。