WinForm特效之桌面上的遮罩层实现方法

using System; 
using System.Drawing; 
using System.Windows.Forms; 
using System.Runtime.InteropServices; 
namespace WindowsApplication40 
{ 
  public partial class Form1 : Form 
  { 
    public Form1() 
    { 
      InitializeComponent(); 
    } 
    [DllImport("user32.dll", EntryPoint = "GetWindowLong")] 
    public static extern long GetWindowLong(IntPtr hwnd, int nIndex); 
 
    [DllImport("user32.dll", EntryPoint = "SetWindowLong")] 
    public static extern long SetWindowLong(IntPtr hwnd, int nIndex, long dwNewLong); 
 
    [DllImport("user32", EntryPoint = "SetLayeredWindowAttributes")] 
    private static extern int SetLayeredWindowAttributes(IntPtr Handle, int crKey, byte bAlpha, int dwFlags); 
 
    const int GWL_EXSTYLE = -20; 
    const int WS_EX_TRANSPARENT = 0x20; 
    const int WS_EX_LAYERED = 0x80000; 
    const int LWA_ALPHA = 2; 
 
 
    private void Form1_Load(object sender, EventArgs e) 
    { 
      this.BackColor = Color.Silver; 
      this.TopMost = true; 
      this.FormBorderStyle = FormBorderStyle.None; 
      this.WindowState = FormWindowState.Maximized; 
      SetWindowLong(Handle, GWL_EXSTYLE, GetWindowLong(Handle, GWL_EXSTYLE) | WS_EX_TRANSPARENT | WS_EX_LAYERED); 
      SetLayeredWindowAttributes(Handle, 0, 128, LWA_ALPHA ); 
 
    } 
  } 
}