c#全局钩子出现有关问题，求解答

c#全局钩子出现问题，求解答！
论坛里看到有讨论全局钩子的，代码大概一致，不过我遇到一个问题：虽然全局钩子能挂上，但是不管我按哪个键返回的值都一样，ncode返回的是0，wparam返回256，lparam返回一串不变的数字，不知道是为啥，麻烦帮我瞅瞅。不胜感激！
代码如下：
public delegate int HOOKPROC(int nCode, int wParam, int lParam);
    public enum HookType
    {
        WH_KEYBOARD = 2,//私有钩子
        WH_KEYBOARD_LL = 13//全局钩子
    }
    public abstract class hook
    {
        //设置钩子
        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
        public static extern int SetWindowsHookEx(HookType idHook, HOOKPROC lpfn, IntPtr hInstance, int threadId);
        //抽调钩子
        [DllImport("user32.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
        public static extern bool UnhookWindowsHookEx(int idHook);

        [DllImport("kernel32")]
        public static extern int GetCurrentThreadId();

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

        /// <summary>
        /// 钩子处理委托
        /// </summary>
        public HOOKPROC proc;
        /// <summary>
        /// 钩子类型
        /// </summary>
        public HookType type;
        /// <summary>
        /// 钩子的句柄
        /// </summary>
        public int hHook = 0;

        public hook(HOOKPROC proc, HookType type)
        {
            this.proc = proc;
            this.type = type;
        }

        public abstract int SetWindowsHookEx();
        public virtual void UnhookWindowsHookEx()
        {
            bool retKeyboard = true;
            if (hHook != 0)
            {
                retKeyboard = UnhookWindowsHookEx(hHook);
                hHook = 0;

            }
            if (!retKeyboard)
            {
                throw new Exception("UnhookWindowsHookEx failed.");
            }
        }
    }
    public class PublicHook : hook
    {
        public PublicHook(HOOKPROC proc)
            : base(proc, HookType.WH_KEYBOARD_LL)
        { }

        public override int SetWindowsHookEx()
        {
            if (hHook == 0)
                //hHook = SetWindowsHookEx(this.type, this.proc, Marshal.GetHINSTANCE(Assembly.GetExecutingAssembly().GetModules()[0]), 0);
                hHook = SetWindowsHookEx(this.type, this.proc, GetModuleHandle(Process.GetCurrentProcess().MainModule.ModuleName), 0);
            return hHook;
        }
    }

    public class PrivateHook : hook
    {
        public PrivateHook(HOOKPROC proc)
            : base(proc, HookType.WH_KEYBOARD)
        { }

        public override int SetWindowsHookEx()
        {
            if (hHook == 0)
                hHook = SetWindowsHookEx(this.type, this.proc, IntPtr.Zero, GetCurrentThreadId());
            return hHook;
        }
    }
[解决办法]

        //Hook结构
        [StructLayout(LayoutKind.Sequential)]
        public class HookStruct
        {
            public int vkCode;
            public int scanCode;
            public int flags;
            public int time;
            public int dwExtraInfo;
        } 
 
        int GetHookCode(int nCode, int wParam, int lParam)
        { //转换结构
            HookStruct hookStruct = (HookStruct)Marshal.PtrToStructure((IntPtr)lParam, typeof(HookStruct));
            MessageBox.Show("您按下了" + (Keys)hookStruct.vkCode);
            return nCode;
        }

  HOOKPROC h = new HOOKPROC(GetHookCode);
            PublicHook hook = new PublicHook(h);
            hook.SetWindowsHookEx();