using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.Diagnostics;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        // For Windows Mobile, replace user32.dll with coredll.dll
        [DllImport("user32.dll", SetLastError = true)]
        static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

        // Find window by Caption only. Note you must pass IntPtr.Zero as the first parameter.

        [DllImport("user32.dll", EntryPoint = "FindWindow", SetLastError = true)]
        static extern IntPtr FindWindowByCaption(IntPtr ZeroOnly, string lpWindowName);
        [DllImport("user32.dll", SetLastError = true)]
static extern int GetWindowLong(IntPtr hWnd, int nIndex);

//sets bigflags that control the windows styles
[DllImport("user32.dll")]
static extern int SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong);
        [DllImport("user32.dll")]
    public static extern IntPtr GetDC(IntPtr hWnd);

//changes flags that modify attributes of the
//layered window such as alpha(opacity)
[DllImport("user32.dll")]
static extern bool SetLayeredWindowAttributes(IntPtr hwnd, uint crKey,
 byte bAlpha, uint dwFlags);
        // You can also call FindWindow(default(string), lpWindowName) or FindWindow((string)null, lpWindowName)
[DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
public static extern IntPtr GetDesktopWindow();
[DllImport("user32.dll")]
public static extern IntPtr SetParent(
     IntPtr hWndChild,      // handle to <strong class="highlight">window</strong>
     IntPtr hWndNewParent   // new parent <strong class="highlight">window</strong>
   );
public const byte AC_SRC_OVER = 0x00;
public const byte AC_SRC_ALPHA = 0x01;
public const Int32 ULW_ALPHA = 0x00000002;
private const short GWL_EXSTYLE = -20;
private const short LWA_ALPHA = 2;
private const short LWA_COLORKEY = 1;
private const int WS_EX_LAYERED = 0x80000;
[StructLayout(LayoutKind.Sequential, Pack = 1)]
public struct BLENDFUNCTION
{
    public byte BlendOp;
    public byte BlendFlags;
    public byte SourceConstantAlpha;
    public byte AlphaFormat;
}
[DllImport("user32.dll", ExactSpelling = true, SetLastError = true)]
public static extern bool UpdateLayeredWindow(IntPtr hwnd, IntPtr hdcDst, ref Point pptDst, ref Size psize, IntPtr hdcSrc, ref Point pprSrc, Int32 crKey, ref BLENDFUNCTION pblend, Int32 dwFlags);
            public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Size size = new Size();
            size.Height = 1000;
            size.Width = 1000;
            IntPtr memDc;
            IntPtr screenDc;
            Point pointSource = new Point(50, 50);
            Point topPos = new Point(0, 500);
            IntPtr foundWindow = new IntPtr(0);
            API.BLENDFUNCTION blend = new API.BLENDFUNCTION();
            Process[] processes = Process.GetProcessesByName("notepad");
            foreach (Process p in processes)
            {
                foundWindow = p.MainWindowHandle;
            }

            memDc = API.GetDC(foundWindow);
            screenDc = API.GetDC(foundWindow);
            SetWindowLong(foundWindow, GWL_EXSTYLE, GetWindowLong(foundWindow, GWL_EXSTYLE) ^ WS_EX_LAYERED);
            API.UpdateLayeredWindow(foundWindow, screenDc, ref topPos, ref size, memDc, ref pointSource, 0, ref blend, 0x00000002);
        }
    }
    internal class API
    {
        public const byte AC_SRC_OVER = 0x00;
        public const byte AC_SRC_ALPHA = 0x01;
        public const Int32 ULW_ALPHA = 0x00000002;

        [StructLayout(LayoutKind.Sequential, Pack = 1)]
        public struct BLENDFUNCTION
        {
            public byte BlendOp;
            public byte BlendFlags;
            public byte SourceConstantAlpha;
            public byte AlphaFormat;
        }

        [DllImport("user32.dll", ExactSpelling = true, SetLastError = true)]
        public static extern bool UpdateLayeredWindow(IntPtr hwnd, IntPtr hdcDst, ref Point pptDst, ref Size psize, IntPtr hdcSrc, ref Point pprSrc, Int32 crKey, ref BLENDFUNCTION pblend, Int32 dwFlags);


        [DllImport("user32.dll", ExactSpelling = true, SetLastError = true)]
        public static extern IntPtr GetDC(IntPtr hWnd);

        [DllImport("gdi32.dll", ExactSpelling = true, SetLastError = true)]
        public static extern IntPtr CreateCompatibleDC(IntPtr hDC);

        [DllImport("user32.dll", ExactSpelling = true)]
        public static extern int ReleaseDC(IntPtr hWnd, IntPtr hDC);

        [DllImport("gdi32.dll", ExactSpelling = true, SetLastError = true)]
        public static extern bool DeleteDC(IntPtr hdc);


        [DllImport("gdi32.dll", ExactSpelling = true)]
        public static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);

        [DllImport("gdi32.dll", ExactSpelling = true, SetLastError = true)]
        public static extern bool DeleteObject(IntPtr hObject);
    }
}