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using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace Tools{
    class Docking {
        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        public static extern IntPtr
        FindWindow([MarshalAs(UnmanagedType.LPTStr)] string lpClassName,
        [MarshalAs(UnmanagedType.LPTStr)] string lpWindowName);

        [DllImport("user32.dll")]
        public static extern IntPtr SetParent(IntPtr hWndChild, IntPtr hWndNewParent);

        /// <summary>
        /// Einzelnes Form auf den Desktop Festkleben
        /// </summary>
        /// <param name="formToDock">Formular, dass an den Desktop gedockt werden soll</param>
        public void StartDocking(Form formToDock) {
            IntPtr hwndParent = FindWindow("progman", null);
            SetParent(formToDock.Handle, hwndParent);
        }
        /// <summary>
        /// Einzelnes Formular vom Desktop wieder lösen und normal anzeigen lassen
        /// </summary>
        /// <param name="formToUndock">Formular das wieder normal angezeigt werden soll</param>
        public void StopDocking(Form formToUndock) {
            IntPtr hwndParent = FindWindow("screenclass", null);
            SetParent(formToUndock.Handle, hwndParent);
        }
    }
}                    

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[DllImport("user32.dll")]
public static extern IntPtr GetDC(long hwnd);                    

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using(Graphics g = Graphics.FromHdc(GetDC(0)))
{
    g.DrawString("Hallo Welt", new Font("Times", 40), Brushes.AliceBlue, new Point(200, 200));
}                    

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[DllImport("user32.dll", CharSet = CharSet.Auto)]
static extern int SystemParametersInfo(
        int Action, int pP, string lpv, int WinIni);                    

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SystemParametersInfo(20, 0, <Pfad>, 1 | 2)