using System;

 using System.Collections.Generic;

 using System.ComponentModel;

 using System.Data;

 using System.Drawing;

 using System.Text;

 using System.Windows.Forms;

 using System.Runtime.InteropServices;

 namespace Demo01

 {

     public partial class Form1 : Form

     {

         public Form1()

         {

             InitializeComponent();

         }

         [DllImport("coredll.dll")]

         public extern static IntPtr GetDesktopWindow();

         [DllImport("coredll.dll")]

         public extern static bool SetLayeredWindowAttributes(IntPtr hwnd, uint crKey, byte bAlpha, uint dwFlags);

         public static uint LWA_COLORKEY = 0x00000001;

         public static uint LWA_ALPHA = 0x00000002;

         [DllImport("coredll.dll")]

         public extern static uint SetWindowLong(IntPtr hwnd, int nIndex, uint dwNewLong);

         [DllImport("coredll.dll")]

         public extern static uint GetWindowLong(IntPtr hwnd, int nIndex);

         public enum WindowStyle : int

         {

             GWL_EXSTYLE = -

         }

         public enum ExWindowStyle : uint

         {

             WS_EX_LAYERED = 0x00080000

         }

         private void SetWindowTransparent(byte bAlpha)

         {

             try

             {

                 SetWindowLong(this.Handle, (int)WindowStyle.GWL_EXSTYLE,

                     GetWindowLong(this.Handle, (int)WindowStyle.GWL_EXSTYLE) | (uint)ExWindowStyle.WS_EX_LAYERED);

                 SetLayeredWindowAttributes(this.Handle, , bAlpha, LWA_ALPHA);

             }

             catch

             {

             }

         }

         private void button1_Click(object sender, EventArgs e)

         {

             this.Close();

         }

         private void trackBar1_ValueChanged(object sender, EventArgs e)

         {

             label1.Text = "透明度(0~255): " + trackBar1.Value.ToString();

             SetWindowTransparent(Convert.ToByte(trackBar1.Value));

         }

         private void Form1_Load(object sender, EventArgs e)

         {

             Rectangle rf = Screen.PrimaryScreen.WorkingArea;

             this.Location = new Point((rf.Width - this.Width) / , (rf.Height - this.Height) / );

             //SetWindowTransparent(136);

         }

     }

 }