全局捕获按键动作

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace MonitorKeys
{
　　//主窗体类
    public partial class Form1 : Form
    {
        UserHook hook = new UserHook();
        bool flag_PullDown = false;

        string front = "";  //组合键的前一个按键
        string tem_s = "";  //组合键
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            hook.KeyDown += new KeyEventHandler(Hook_KeyDown);
            hook.KeyUp += new KeyEventHandler(Hook_KeyUp);

            if(hook.Start() ==true)
            {
                MessageBox.Show("检测进程启动成功!");
            }
            else
            {
                MessageBox.Show("检测进程启动失败!");
            }
        }
        void Hook_KeyDown(object send,KeyEventArgs e)
        {
            AddKeyboardEvent("KeyDown", e.KeyCode.ToString(), "", e.Shift.ToString(), e.Alt.ToString(), e.Control.ToString());
        }
        void Hook_KeyUp(object send, KeyEventArgs e)
        {
            AddKeyboardEvent("KeyUp", e.KeyCode.ToString(), "", e.Shift.ToString(), e.Alt.ToString(), e.Control.ToString());
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="eventType">按键类型</param>
        /// <param name="keyCode">键名称</param>
        /// <param name="keyChar">键值</param>
        /// <param name="shift">是否为Shift键</param>
        /// <param name="alt">是否为Alt键</param>
        /// <param name="control">是否为Ctrl键</param>
        public void AddKeyboardEvent(string eventType,string keyCode,string keyChar,string shift,string alt,string control)
        {
            //tem_s = 0;
            bool b = false;
            string keyValue = "";
            GetKey(keyCode, out b, out keyValue);

            if(eventType=="KeyDown")
            {
                flag_PullDown = true;
            }
            if(eventType=="KeyUp")  //完成组合键：1.清除有键按下的状态 2.清除组合键记录(先显示，后清除) 3.清除前键值记录
            {
                if (tem_s != "")
                {
                    textBox1.Text = tem_s;                 
                }
                //else 
                //{
                //    textBox1.Text = front;           
                //}
                
                flag_PullDown = false;
                front = "";
                tem_s = "";               
            }
            if((flag_PullDown==true)&&(eventType=="KeyDown"))
            {
                //前一键与当前键是否一致，一致则不进行处理，不一致则进行记录
                if(front!=keyValue)     //判定是否为组合键：是(true) 否(false)
                {
                    if (front == "")
                    {
                        tem_s = keyValue;
                    }
                    else
                    {
                        tem_s += "+" + keyValue;
                    }
                }
               front = keyValue;
            }
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="k">键名称</param>
        /// <param name="b">是否有热键</param>
        /// <param name="keyValue">当前热键名称</param>
        public void GetKey(string k,out bool b,out string keyValue)
        {
            if(k.Contains("ControlKey"))
            {
                b = true;
                keyValue = "Ctrl";
                return;
            }
            if (k.Contains("Shift"))
            {
                b = true;
                keyValue = "Shift";
                return;
            }
            if (k.Contains("Alt"))
            {
                b = true;
                keyValue = "Alt";
                return;
            }
            if (k.Contains("Win"))
            {
                b = true;
                keyValue = "Win";
                return;
            }

            b = true;
            keyValue = k;

        }

        private void Form1_FormClosed(object sender, FormClosedEventArgs e)
        {
            if(hook!=null)
            {
                hook.Stop();
            }
        }

        private void ShowInfo(string info)
        {
            MessageBox.Show(info);
        }

        private void btn_Open_Click(object sender, EventArgs e)
        {
            if(hook.isInstalled==false)
            {
                hook.Start();
            }           
        }

        private void btn_Stop_Click(object sender, EventArgs e)
        {
            if (hook != null)
            {
                hook.Stop();
            }
        }
    }
}

消息捕获类：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace MonitorKeys
{
    class UserHook
    {
        private const int WH_KEYBOARD_LL = 13;
        private const int WM_KEYDOWN = 0X0100;
        private const int WM_KEYSYSKEYDOWN = 0X0104;
        private const int WM_KEYUP = 0X0101;
        private const int WM_KEYSYSKEYUP = 0X0105;

        public delegate int HookProc(int nCode, Int32 wParam, IntPtr Iparam);

        [DllImport("user32.dll")]   //参数列表(钩子类型，钩子函数入口地址，钩子所在的实例句柄，钩子监视的线程号)
        public static extern IntPtr SetWindowsHookEx(int HookType, HookProc methodAddress, IntPtr handler, int dwThreadId);

        [DllImport("user32.dll")]   //参数列表(钩子所在的实例句柄)
        public static extern bool UnhookWindowsHookEx(IntPtr idHook);

        [DllImport("kernel32.dll")]
        public static extern IntPtr GetModuleHandle(string name);

        IntPtr p_Hook = IntPtr.Zero;            //钩子句柄
        IntPtr p_Keyboard = IntPtr.Zero;        //键盘的消息句柄

        HookProc keyboardHookProcedure;     //处理键盘信息的钩子
        [StructLayout(LayoutKind.Sequential)]
        public class KeyMSG
        {
            public int vkCode;      //定义一个虚拟键码(1-254之间)
            public int scanCode;    //指定硬件的扫描码
            public int flags;       //键标识
            public int times;       //信息的时间戳
            public int dwExtrainfo; //额外信息
        }


        public event KeyEventHandler KeyPress;
        public event KeyEventHandler KeyDown;
        public event KeyEventHandler KeyUp;

        public bool isInstalled = false;

        public bool Start()
        {
            //p_Hook = (IntPtr)4194304;       //定义钩子句柄;

            p_Hook = GetModuleHandle(System.Diagnostics.Process.GetCurrentProcess().MainModule.ModuleName);
            if(p_Keyboard==IntPtr.Zero)     //键盘句柄是否为空
            {
                keyboardHookProcedure = new HookProc(KeyboardHookProc);
                p_Keyboard = SetWindowsHookEx(WH_KEYBOARD_LL, keyboardHookProcedure, p_Hook, 0);    //安装钩子(将"钩子的句柄"与"键盘消息句柄"进行绑定)
                if(p_Keyboard==IntPtr.Zero)
                {
                    this.Stop();
                    return false;
                }
            }
            isInstalled = true;
            return true;
        }
        public bool Stop()
        {
            if(isInstalled==false)
            {
                return true;
            }
            bool result = true;
            if(this.p_Keyboard!=IntPtr.Zero)
            {
                result = UnhookWindowsHookEx(this.p_Keyboard);
                this.p_Keyboard = IntPtr.Zero;
            }
            return result;
        }
        

        private int KeyboardHookProc(int nCode, Int32 wParam, IntPtr Iparam)
        {
            if(nCode>-1&&((KeyPress!=null)||(KeyDown!=null)||(KeyUp!=null)))
            {
                KeyMSG keybaoardHookStruct = (KeyMSG)Marshal.PtrToStructure(Iparam, typeof(KeyMSG));
                KeyEventArgs e = new KeyEventArgs((Keys)(keybaoardHookStruct.vkCode));
                switch(wParam)
                {
                    case WM_KEYDOWN:
                    case WM_KEYSYSKEYDOWN:
                        KeyDown.Invoke(this, e);
                        break;

                    case WM_KEYUP:
                    case WM_KEYSYSKEYUP:
                        KeyUp.Invoke(this, e);
                        break;
                }
            }
            return 0;
        }
    }
}

UI视图：

(注意：清空的功能，是V0.2版添加的，需要在主窗体代码中补写)