监听键盘事件
在程序启动的时候如何监听键盘事件,请高手给个事例;

------解决方案--------------------
钩子函数,比较容易,网上资料多的是
得到鼠标的消息的类：using System;
using System.Runtime.InteropServices;
using System.Reflection;
using System.Threading;
using System.Windows.Forms;
namespace HookGlobal
{
/// <summary>
/// 这个类可以让你得到一个在运行中程序的所有鼠标事件
/// 并且引发一个带MouseEventArgs参数的.NET鼠标事件以便你很容易使用这些信息
/// </summary>
public class MouseHook
{
private const int WM_MOUSEMOVE = 0x200;
private const int WM_LBUTTONDOWN = 0x201;
private const int WM_RBUTTONDOWN = 0x204;
private const int WM_MBUTTONDOWN = 0x207;
private const int WM_LBUTTONUP = 0x202;
private const int WM_RBUTTONUP = 0x205;
private const int WM_MBUTTONUP = 0x208;
private const int WM_LBUTTONDBLCLK = 0x203;
private const int WM_RBUTTONDBLCLK = 0x206;
private const int WM_MBUTTONDBLCLK = 0x209;
//全局的事件
public event MouseEventHandler OnMouseActivity;
static int hMouseHook = 0; //鼠标钩子句柄
//鼠标常量
public const int WH_MOUSE_LL = 14; //mouse hook constant
HookProc MouseHookProcedure; //声明鼠标钩子事件类型.
//声明一个Point的封送类型
[StructLayout(LayoutKind.Sequential)]
public class POINT
{
public int x;
public int y;
}
//声明鼠标钩子的封送结构类型
[StructLayout(LayoutKind.Sequential)]
public class MouseHookStruct
{
public POINT pt;
public int hWnd;
public int wHitTestCode;
public int dwExtraInfo;
}
//装置钩子的函数
[DllImport( "user32.dll ",CharSet=CharSet.Auto, CallingConvention=CallingConvention.StdCall)]
public static extern int SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hInstance, int threadId);
//卸下钩子的函数
[DllImport( "user32.dll ",CharSet=CharSet.Auto, CallingConvention=CallingConvention.StdCall)]
public static extern bool UnhookWindowsHookEx(int idHook);

//下一个钩挂的函数
[DllImport( "user32.dll ",CharSet=CharSet.Auto, CallingConvention=CallingConvention.StdCall)]
public static extern int CallNextHookEx(int idHook, int nCode, Int32 wParam, IntPtr lParam);
public delegate int HookProc(int nCode, Int32 wParam, IntPtr lParam);
/// <summary>
/// 墨认的构造函数构造当前类的实例.
/// </summary>
public MouseHook()
{
//Start();
}
//析构函数.
~MouseHook()
{
Stop();
}
public void Start()
{
//安装鼠标钩子
if(hMouseHook == 0)
{
//生成一个HookProc的实例.
MouseHookProcedure = new HookProc(MouseHookProc);
hMouseHook = SetWindowsHookEx( WH_MOUSE_LL, MouseHookProcedure, Marshal.GetHINSTANCE(Assembly.GetExecutingAssembly().GetModules()[0]), 0);
//如果装置失败停止钩子
if(hMouseHook == 0 )
{
Stop();
throw new Exception( "SetWindowsHookEx failed. ");
}
}
}
public void Stop()
{
bool retMouse =true;
if(hMouseHook != 0)
{
retMouse = UnhookWindowsHookEx(hMouseHook);
hMouseHook = 0;
}

//如果卸下钩子失败
if (!(retMouse)) throw new Exception( "UnhookWindowsHookEx failed. ");
}
private int MouseHookProc(int nCode, Int32 wParam, IntPtr lParam)
{
//如果正常运行并且用户要监听鼠标的消息
if ((nCode > = 0) && (OnMouseActivity!=null))
{
MouseButtons button=MouseButtons.None;
int clickCount=0;
switch (wParam)
{
case WM_LBUTTONDOWN:
button=MouseButtons.Left;
clickCount=1;
break;
case WM_LBUTTONUP: