Switch taskbar aute hide state.

TaskbarHelper.cs

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;

internal static class TaskbarHelper
{
    [DllImport("user32.dll", CharSet = CharSet.Unicode)]
    extern static IntPtr FindWindow(
        [MarshalAs(UnmanagedType.LPWStr), In] string lpClassName,
        [MarshalAs(UnmanagedType.LPWStr), In] string? lpWindowName);

    [DllImport("shell32.dll", CharSet = CharSet.Unicode)]
    extern static UIntPtr SHAppBarMessage(
        uint dwMessage,
        ref APPBARDATA pData);

    [StructLayout(LayoutKind.Sequential)]
    struct APPBARDATA
    {
        public uint cbSize;
        public IntPtr hWnd;
        public int uCallbackMessage;
        public int uEdge;
        public RECT rc;
        public IntPtr lParam;
    }

    [StructLayout(LayoutKind.Sequential)]
    struct RECT
    {
        public int Left;
        public int Top;
        public int Right;
        public int Bottom;
    }

    const uint ABM_GETSTATE = 0x00000004;
    const uint ABM_SETSTATE = 0x0000000A;

    const uint ABS_AUTOHIDE = 0x01;
    const uint ABS_ALWAYSONTOP = 0x02;

    public static void SwitchState()
    {
        var taskbarHandle = FindWindow("System_TrayWnd", null);

        var status = GetStatus(taskbarHandle);
        switch (status)
        {
            case ABS_AUTOHIDE:
                Trace.WriteLine("To always on top");
                SetStatus(taskbarHandle, ABS_ALWAYSONTOP);
                break;

            case ABS_ALWAYSONTOP:
            default:
                Trace.WriteLine("To auto hide");
                SetStatus(taskbarHandle, ABS_AUTOHIDE);
                break;
        }
    }

    private static uint GetStatus(IntPtr handle)
    {
        var data = new APPBARDATA { hWnd = handle };
        data.cbSize = (uint)Marshal.SizeOf(data);
        return (uint)SHAppBarMessage(ABM_GETSTATE, ref data);
    }

    private static void SetStatus(IntPtr handle, uint option)
    {
        var data = new APPBARDATA { hWnd = handle, lParam = (int)option };
        data.cbSize = (uint)Marshal.SizeOf(data);
        SHAppBarMessage(ABM_SETSTATE, ref data);
    }
}