using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;

namespace you_name
{
    internal class taskbar
    {
        [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 =
            0x00000000,
            Remove =
            0x00000001,
            QueryPos =
            0x00000002,
            SetPos =
            0x00000003,
            GetState =
            0x00000004,
            GetTaskBarPos =
            0x00000005,
            Activate =
            0x00000006,
            GetAutoHideBar =
            0x00000007,
            SetAutoHideBar =
            0x00000008,
            WindowPosChanged =
            0x00000009,
            SetState =
            0x0000000a
        }

        [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 =
            0x00000001,
            AlwaysOnTop =
            0x00000002
        }

        /// <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();