How to toggle/switch Windows taskbar from "show" to "auto-hide" (and vice-versa)?

Question

Basically I want to make simple toggle program (that will be mapped to some keyboard shortcut) that set taskbar to auto-hide mode if in normal mode (and conversely, to normal show mode if in auto-hide).

Do You know how to implement it in C#? (or Win32 C++, but anything that will actually do it is fine.)

Thanks. Hope I've made myself clear.

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I don't really want any full screen app that will overlap taskbar, only windowless program that toggles show mode and quit. I switch from auto-hide to normal view on regular basis and want to simplify it. (Using Win7.)

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edited. For example

#include <windows.h>

int CALLBACK WinMain(HINSTANCE, HINSTANCE, LPSTR, int)
{
    SetWindowPos(FindWindow(L"Shell_traywnd", NULL ), 0, 0, 0, 0, 0, 0x40);
}

will not do the trick, it only shows taskbar, which is already visible=true, but not switch it to/from auto-hide. (Same applies for 0x80.)

Answer 1

Here are the functions I use:

[DllImport("user32.dll", CharSet = CharSet.Auto)]
public static extern IntPtr FindWindow(string strClassName, string strWindowName);

[DllImport("shell32.dll")]
public static extern UInt32 SHAppBarMessage(UInt32 dwMessage, ref APPBARDATA pData);

public enum AppBarMessages
{
    New              = 0x00,
    Remove           = 0x01,
    QueryPos         = 0x02,
    SetPos           = 0x03,
    GetState         = 0x04,
    GetTaskBarPos    = 0x05,
    Activate         = 0x06,
    GetAutoHideBar   = 0x07,
    SetAutoHideBar   = 0x08,
    WindowPosChanged = 0x09,
    SetState         = 0x0a
}

[StructLayout(LayoutKind.Sequential)]
public struct APPBARDATA
{
    public UInt32 cbSize;
    public IntPtr hWnd;
    public UInt32 uCallbackMessage;
    public UInt32 uEdge;
    public Rectangle rc;
    public Int32 lParam;
}

public enum AppBarStates
{
    AutoHide    = 0x01,
    AlwaysOnTop = 0x02
}

/// <summary>
/// Set the Taskbar State option
/// </summary>
/// <param name="option">AppBarState to activate</param>
public void SetTaskbarState(AppBarStates option)
{
    APPBARDATA msgData = new APPBARDATA();
    msgData.cbSize = (UInt32)Marshal.SizeOf(msgData);
    msgData.hWnd = FindWindow("System_TrayWnd", null);
    msgData.lParam = (Int32)(option);
    SHAppBarMessage((UInt32)AppBarMessages.SetState, ref msgData);
}

/// <summary>
/// Gets the current Taskbar state
/// </summary>
/// <returns>current Taskbar state</returns>
public AppBarStates GetTaskbarState()
{
    APPBARDATA msgData = new APPBARDATA();
    msgData.cbSize = (UInt32)Marshal.SizeOf(msgData);
    msgData.hWnd = FindWindow("System_TrayWnd", null);
    return (AppBarStates)SHAppBarMessage((UInt32)AppBarMessages.GetState, ref msgData);
}

When the code above is implemented just set the Taskbar to autohide by: SetTaskbarState(AppBarStates.AutoHide);

Get the current state by:

AppBarStates currentState = GetTaskbarState();