关键词'；这'；在静态属性、静态方法或静态字段初始值设定项中无效

我使用以下代码：

 public partial class ThisAddIn
{
    private const int WH_KEYBOARD_LL = 13;
    private const int WM_KEYDOWN = 0x0100;
    private static IntPtr hookId = IntPtr.Zero;
    private delegate IntPtr HookProcedure(int nCode, IntPtr wParam, IntPtr lParam);
    private static HookProcedure procedure = HookCallback;
    [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern IntPtr GetModuleHandle(string lpModuleName);
    [DllImport("user32.dll", SetLastError = true)]
    private static extern bool UnhookWindowsHookEx(IntPtr hhk);
    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern IntPtr SetWindowsHookEx(int idHook, HookProcedure lpfn, IntPtr hMod, uint dwThreadId);
    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode, IntPtr wParam, IntPtr lParam);
    private void ThisAddIn_Startup(object sender, System.EventArgs e)
    {
        hookId = SetHook(procedure);
    }
    private void ThisAddIn_Shutdown(object sender, System.EventArgs e)
    {
        UnhookWindowsHookEx(hookId); 
    }
    private static IntPtr SetHook(HookProcedure procedure)
    {
        using (Process process = Process.GetCurrentProcess())
        using (ProcessModule module = process.MainModule)
            return SetWindowsHookEx(WH_KEYBOARD_LL, procedure, GetModuleHandle(module.ModuleName), 0);
    }
    private static IntPtr HookCallback(int nCode, IntPtr wParam, IntPtr lParam)
    {
        if (nCode >= 0 && wParam == (IntPtr)WM_KEYDOWN)
        {
            int pointerCode = Marshal.ReadInt32(lParam);
            string pressedKey = ((Keys)pointerCode).ToString();
            //Do some sort of processing on key press
            var thread = new Thread(() => 
            {   MessageBox.Show(pressedKey);
                if (pressedKey.Equals("Space") || pressedKey.Equals("Tab"))
                    {
                        ***Word.Range rng = this.Application.ActiveDocument.Words.Last;
                        rng.Select();
                        rng.Copy();
                        String input = Clipboard.GetText(TextDataFormat.Text);
                    }               
            });
            thread.Start();
        }
        return CallNextHookEx(hookId, nCode, wParam, lParam);
    }
    private void InternalStartup()
    {
        this.Startup += new System.EventHandler(ThisAddIn_Startup);
        this.Shutdown += new System.EventHandler(ThisAddIn_Shutdown);
    }
}

我收到以下标有***的行的错误：

错误1关键字"this"在静态属性中无效，static方法或静态字段初始值设定项。

请告知

private static IntPtr HookCallback(int nCode, IntPtr wParam, IntPtr lParam)
{
    if (nCode >= 0 && wParam == (IntPtr)WM_KEYDOWN)
    {
        int pointerCode = Marshal.ReadInt32(lParam);
        string pressedKey = ((Keys)pointerCode).ToString();
        //Do some sort of processing on key press
        var thread = new Thread(() => 
        {   MessageBox.Show(pressedKey);
            if (pressedKey.Equals("Space") || pressedKey.Equals("Tab"))
                {
                    ***Word.Range rng = this.Application.ActiveDocument.Words.Last;
                    rng.Select();
                    rng.Copy();
                    String input = Clipboard.GetText(TextDataFormat.Text);
                }               
        });
        thread.Start();
    }
    return CallNextHookEx(hookId, nCode, wParam, lParam);
}