因此，经过长时间的搜索，我终于找到了这个问题的答案。诀窍是使用dwmapi.dll的DwmSetWindowAttribute，并将未记录的常量DWMWA_USE_IMMERSIVE_DARK_MODE传递到函数中。在C#中，用于此操作的代码看起来有点像这样（既适用于WinForms，也适用于WPF）：

/*
using System.Runtime.InteropServices;
*/

[DllImport("dwmapi.dll")]
private static extern int DwmSetWindowAttribute(IntPtr hwnd, int attr, ref int attrValue, int attrSize);

private const int DWMWA_USE_IMMERSIVE_DARK_MODE_BEFORE_20H1 = 19;
private const int DWMWA_USE_IMMERSIVE_DARK_MODE = 20;

private static bool UseImmersiveDarkMode(IntPtr handle, bool enabled)
{
    if (IsWindows10OrGreater(17763))
    {
        var attribute = DWMWA_USE_IMMERSIVE_DARK_MODE_BEFORE_20H1;
        if (IsWindows10OrGreater(18985))
        {
            attribute = DWMWA_USE_IMMERSIVE_DARK_MODE;
        }

        int useImmersiveDarkMode = enabled ? 1 : 0;
        return DwmSetWindowAttribute(handle, (int)attribute, ref useImmersiveDarkMode, sizeof(int)) == 0;
    }

    return false;
}

private static bool IsWindows10OrGreater(int build = -1)
{
    return Environment.OSVersion.Version.Major >= 10 && Environment.OSVersion.Version.Build >= build;
}

最快的道：

[DllImport("DwmApi")] //System.Runtime.InteropServices
private static extern int DwmSetWindowAttribute(IntPtr hwnd, int attr, int[] attrValue, int attrSize);

protected override void OnHandleCreated(EventArgs e)
{
    if (DwmSetWindowAttribute(Handle, 19, new[] { 1 }, 4) != 0)
        DwmSetWindowAttribute(Handle, 20, new[] { 1 }, 4);
}

对于Jonas Kohl提供的解决方案，请记住，对于.net fw 4.8.1和更早版本，返回的版本不正确，已在.Net6中修复，此处是一个片段（.Net 5不受管）：

private static bool IsWindows10OrGreater(int build = -1)
    {
        return WindowsVersion() >= 10 && WindowsBuildNumber() >= build;
    }

    public static int WindowsVersion()
    {
     //for .Net4.8 and Minor
     #if NETFRAMEWORK
        int result = 10;
        var reg = Registry.LocalMachine.OpenSubKey(@"SOFTWARE\Microsoft\Windows NT\CurrentVersion");
        string[] productName = reg.GetValue("ProductName").ToString().Split((char)32);
        int.TryParse(productName[1], out result);
        return result;
     #else
        //fixed in .Net6
        return System.Environment.OSVersion.Version.Major;
     #endif
    }

    public static int WindowsBuildNumber()
    {
        //for .Net4.8 and Minor
    #if NETFRAMEWORK
        int result = 22000;
        var reg = Registry.LocalMachine.OpenSubKey(@"SOFTWARE\Microsoft\Windows NT\CurrentVersion");
        string buildNumber = reg.GetValue("CurrentBuildNumber").ToString();
        int.TryParse(buildNumber, out result);
        return result;
    #endif

    #if NET
        //fixed in .Net6
        return System.Environment.OSVersion.Version.Build;
    #endif
    }