C# 全局鉤子本身不直接支持異步操作。全局鉤子通常用于監聽鍵盤、鼠標等輸入事件，這些事件需要實時處理，因此通常使用同步方法。然而，你可以在全局鉤子的回調函數中使用異步操作。

以下是一個使用 C# 全局鉤子并在回調函數中使用異步操作的示例：

using System;
using System.Threading.Tasks;
using System.Windows.Forms;

public class GlobalHookExample
{
    private static LowLevelKeyboardProc _keyboardProc;
    private static IntPtr _hookID = IntPtr.Zero;

    public static void Main()
    {
        _keyboardProc = KeyboardHookCallback;
        _hookID = SetHook(_keyboardProc);

        Application.Run();

        UnhookWindowsHookEx(_hookID);
    }

    private static IntPtr SetHook(LowLevelKeyboardProc proc)
    {
        using (var curProcess = System.Diagnostics.Process.GetCurrentProcess())
        using (var curModule = curProcess.MainModule)
        {
            return SetWindowsHookEx(WH_KEYBOARD_LL, proc, GetModuleHandle(curModule.ModuleName), 0);
        }
    }

    private delegate IntPtr LowLevelKeyboardProc(int nCode, IntPtr wParam, IntPtr lParam);

    private static IntPtr KeyboardHookCallback(int nCode, IntPtr wParam, IntPtr lParam)
    {
        if (nCode >= 0 && wParam == (IntPtr)WM_KEYDOWN)
        {
            int vkCode = Marshal.ReadInt32(lParam);
            Task.Run(() => HandleKeyDownAsync((Keys)vkCode));
        }

        return CallNextHookEx(_hookID, nCode, wParam, lParam);
    }

    private static async Task HandleKeyDownAsync(Keys key)
    {
        // 在這里處理按鍵事件，例如：
        await Task.Delay(1000);
        Console.WriteLine($"Key pressed: {key}");
    }

    private const int WH_KEYBOARD_LL = 13;
    private const int WM_KEYDOWN = 0x0100;

    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern IntPtr SetWindowsHookEx(int idHook, LowLevelKeyboardProc lpfn, IntPtr hMod, uint dwThreadId);

    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool UnhookWindowsHookEx(IntPtr hhk);

    [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode, IntPtr wParam, IntPtr lParam);

    [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern IntPtr GetModuleHandle(string lpModuleName);
}

在這個示例中，我們創建了一個全局鍵盤鉤子，當按鍵事件發生時，KeyboardHookCallback 函數會被調用。在這個函數中，我們使用 Task.Run 將 HandleKeyDownAsync 函數作為異步任務運行。這樣，HandleKeyDownAsync 函數中的代碼將在后臺線程上執行，而不會阻塞主線程。