代码说明

• ImmGetDefaultIMEWnd：获取默认的 IME 窗口句柄。
• ImmIsIME：检查当前的键盘布局是否是 IME。
• LoadKeyboardLayout：加载指定的键盘布局（如英语）。
• GetForegroundWindow：获取当前前景窗口的句柄。
• GetKeyboardLayout：获取当前线程的键盘布局。
• KLF_ACTIVATE：激活键盘布局的标志。
• ENGLISH_KEYBOARD_LAYOUT：英语（美国）的键盘布局 ID（00000409）。

using System;
using System.Runtime.InteropServices;
using System.Text;

class Program
{
    // 声明 Windows API 函数
    [DllImport("imm32.dll", CharSet = CharSet.Auto)]
    private static extern IntPtr ImmGetDefaultIMEWnd(IntPtr hWnd);

    [DllImport("imm32.dll", CharSet = CharSet.Auto)]
    private static extern bool ImmIsIME(IntPtr hKL);

    [DllImport("imm32.dll", CharSet = CharSet.Auto)]
    private static extern IntPtr ImmGetContext(IntPtr hWnd);

    [DllImport("imm32.dll", CharSet = CharSet.Auto)]
    private static extern bool ImmSetOpenStatus(IntPtr hIMC, bool bOpen);

    [DllImport("imm32.dll", CharSet = CharSet.Auto)]
    private static extern bool ImmReleaseContext(IntPtr hWnd, IntPtr hIMC);

    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    private static extern IntPtr GetKeyboardLayout(uint idThread);

    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    private static extern IntPtr LoadKeyboardLayout(string pwszKLID, uint Flags);

    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    private static extern bool UnloadKeyboardLayout(IntPtr hkl);

    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    private static extern IntPtr GetForegroundWindow();

    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    private static extern uint GetWindowThreadProcessId(IntPtr hWnd, IntPtr lpdwProcessId);

    // 定义键盘布局常量
    private const uint KLF_ACTIVATE = 0x00000001;
    private const string ENGLISH_KEYBOARD_LAYOUT = "00000409"; // 英语（美国）的键盘布局 ID

    static void Main(string[] args)
    {
        // 获取当前前景窗口的句柄
        IntPtr hWnd = GetForegroundWindow();

        // 获取当前线程的键盘布局
        uint threadId = GetWindowThreadProcessId(hWnd, IntPtr.Zero);
        IntPtr hKL = GetKeyboardLayout(threadId);

        // 检查当前键盘布局是否是 IME
        if (ImmIsIME(hKL))
        {
            Console.WriteLine("当前输入法是 IME，正在切换到英语输入法...");

            // 加载英语键盘布局
            IntPtr englishLayout = LoadKeyboardLayout(ENGLISH_KEYBOARD_LAYOUT, KLF_ACTIVATE);

            if (englishLayout != IntPtr.Zero)
            {
                Console.WriteLine("已切换到英语输入法。");
            }
            else
            {
                Console.WriteLine("无法加载英语键盘布局。");
            }
        }
        else
        {
            Console.WriteLine("当前输入法已经是非 IME 输入法（如英语）。");
        }
    }
}