using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
using System.Drawing;


namespace MBoxNewDesktop
{
    using System.Runtime.InteropServices;
    using System.Windows.Forms;
    using System.Drawing;
    using System.Threading;
    using System.Diagnostics;

    class ShowSystemModalMBOX
    {
        internal sealed class Native
        {
            // Fields
            public const int DESKTOP_SWITCHDESKTOP = 0x100;
            public const int GENERIC_ALL = 0x10000000;

            [return: MarshalAs(UnmanagedType.Bool)]
            [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
            public static extern bool CloseDesktop(IntPtr desktop);
            [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
            public static extern IntPtr CreateDesktop([MarshalAs(UnmanagedType.VBByRefStr)] ref string desktop, [MarshalAs(UnmanagedType.VBByRefStr)] ref string device, IntPtr devmode, int flags, int desiredAccess, IntPtr lpsa);
            [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
            public static extern IntPtr GetThreadDesktop(int threadId);
            [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
            public static extern IntPtr OpenInputDesktop(int flags, [MarshalAs(UnmanagedType.Bool)] bool inherit, int desiredAccess);
            [return: MarshalAs(UnmanagedType.Bool)]
            [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
            public static extern bool SetThreadDesktop(IntPtr desktop);
            [return: MarshalAs(UnmanagedType.Bool)]
            [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
            public static extern bool SwitchDesktop(IntPtr desktop);
        }


        public void Show()
        {
            this.LockSystemAndShow(new Form(), delegate (){
                MessageBox.Show("Nachricht mit Vista Effekt", "Beschreibung", MessageBoxButtons.YesNoCancel);
            });   
        }

        public delegate void EmptyHandler();
        private bool LockSystemAndShow(Form window, EmptyHandler method)
        {
            Control owner = window;
            Screen screen = owner == null ? Screen.PrimaryScreen : Screen.FromControl(owner);
            Bitmap image = new Bitmap(screen.Bounds.Width, screen.Bounds.Height);
            using (Graphics graphics = Graphics.FromImage(image))
            {
                IntPtr ptr4 = IntPtr.Zero;
                Rectangle bounds = screen.Bounds;
                graphics.CopyFromScreen(0, 0, 0, 0, bounds.Size);
                using (Brush brush = new SolidBrush(Color.FromArgb(0xc0, Color.Black)))
                {
                    graphics.FillRectangle(brush, screen.Bounds);
                }
                if (owner != null)
                {
                    Form form = owner.FindForm();
                    graphics.CopyFromScreen(form.Location, form.Location, form.Size);
                    using (Brush brush2 = new SolidBrush(Color.FromArgb(0x80, Color.Black)))
                    {
                        bounds = new Rectangle(form.Location, form.Size);
                        graphics.FillRectangle(brush2, bounds);
                    }
                }
                IntPtr threadDesktop = Native.GetThreadDesktop(Thread.CurrentThread.ManagedThreadId);
                IntPtr newThreadDesktop = Native.OpenInputDesktop(0, false, 0x100);
                string device = null;
                string avar = "Desktop" + Guid.NewGuid().ToString();
                IntPtr ptr = Native.CreateDesktop(ref avar, ref device, ptr4, 0, 0x10000000, ptr4);
                Native.SetThreadDesktop(ptr);
                Native.SwitchDesktop(ptr);
                Thread thread = new Thread(new ParameterizedThreadStart(this.ShowBackgroundThreadMethod));
                thread.Start(new LockSystemParameters(ptr, image, method));
                thread.Join();
                Native.SwitchDesktop(newThreadDesktop);
                Native.SetThreadDesktop(threadDesktop);
                Native.CloseDesktop(ptr);
                return false;
            }
        }

        private class LockSystemParameters
        {
            public Bitmap Background;
            public IntPtr DesktopPointer;
            public EmptyHandler Method;
            public LockSystemParameters(IntPtr desktopPtr, Bitmap background, EmptyHandler method)
            {
                this.Background = background;
                this.DesktopPointer = desktopPtr;
                this.Method = method;
            }
        }

        private void ShowBackgroundThreadMethod(object aparams)
        {
            LockSystemParameters parameters = (LockSystemParameters)aparams;
            Native.SetThreadDesktop(parameters.DesktopPointer);
            using (Form form = new BackgroundForm(parameters.Background))
            {
                form.Show();
                parameters.Method.DynamicInvoke(null); // STARTE DEN FensterDarstellung
                form.BackgroundImage = null;
                Application.DoEvents();
                Thread.Sleep(250);
            }
        }

        public class BackgroundForm : Form
        {
            // Fields
            private Bitmap background;

            // Methods
            public BackgroundForm(Bitmap background)
            {
                this.BackColor = Color.Black;
                this.FormBorderStyle = FormBorderStyle.None;
                this.Location = Point.Empty;
                this.Size = Screen.PrimaryScreen.Bounds.Size;
                this.StartPosition = FormStartPosition.Manual;
                this.Visible = true;
                this.background = background;
            }

            protected override void OnShown(EventArgs e)
            {
                this.BackgroundImage = this.background;
                this.DoubleBuffered = true;
                base.OnShown(e);
            }
        }

        static void Main(string[] args)
        {
            ShowSystemModalMBOX p = new ShowSystemModalMBOX();
            p.Show();
        }
    }
}