c# winform窗口一直置顶显示在桌面最上方或最底层的方法

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 ShowInDesk 
{ 
publicpartialclass Form1 : Form 
{ 
IntPtr hDesktop; 
publicconstint GW_CHILD =5; 
public Form1() 
{ 
InitializeComponent(); 
this.hDesktop = GetDesktopHandle(DesktopLayer.Progman); 
EmbedDesktop(this, this.Handle, this.hDesktop); 
isMouseDown =false; 
} 
public IntPtr GetDesktopHandle(DesktopLayer layer) { //hWnd = new HandleRef(); 
HandleRef hWnd; 
IntPtr hDesktop =new IntPtr(); 
switch (layer) 
{ 
case DesktopLayer.Progman: 
hDesktop = Win32Support.FindWindow("Progman", null);//第一层桌面 
break; 
case DesktopLayer.SHELLDLL: 
hDesktop = Win32Support.FindWindow("Progman", null);//第一层桌面 
hWnd =new HandleRef(this, hDesktop); 
hDesktop = Win32Support.GetWindow(hWnd, GW_CHILD);//第2层桌面 
break; 
case DesktopLayer.FolderView: 
hDesktop = Win32Support.FindWindow("Progman", null);//第一层桌面 
hWnd =new HandleRef(this, hDesktop); 
hDesktop = Win32Support.GetWindow(hWnd, GW_CHILD);//第2层桌面 
hWnd =new HandleRef(this, hDesktop); 
hDesktop = Win32Support.GetWindow(hWnd, GW_CHILD);//第3层桌面 
break; 
} 
return hDesktop; 
} 
publicvoid EmbedDesktop(Object embeddedWindow, IntPtr childWindow, IntPtr parentWindow) 
{ 
Form window = (Form)embeddedWindow; 
HandleRef HWND_BOTTOM =new HandleRef(embeddedWindow, new IntPtr(1)); 
constint SWP_FRAMECHANGED =0x0020;//发送窗口大小改变消息 
Win32Support.SetParent(childWindow, parentWindow); 
Win32Support.SetWindowPos(new HandleRef(window, childWindow), HWND_BOTTOM, 300, 300, window.Width, window.Height, SWP_FRAMECHANGED); 
} 
} 
} 

using System; 
using System.Collections.Generic; 
using System.Text; 
using System.Runtime.InteropServices; 
namespace ShowInDesk 
{ 
class Win32Support 
{ 
[DllImport("user32.dll", CharSet = CharSet.Auto)] 
publicstaticextern IntPtr FindWindow(string className, string windowName); 
[DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling =true)] 
publicstaticextern IntPtr GetWindow(HandleRef hWnd, int nCmd); 
[DllImport("user32.dll")] 
publicstaticextern IntPtr SetParent(IntPtr child, IntPtr parent); 
[DllImport("user32.dll", EntryPoint ="GetDCEx", CharSet = CharSet.Auto, ExactSpelling =true)] 
publicstaticextern IntPtr GetDCEx(IntPtr hWnd, IntPtr hrgnClip, int flags); 
[DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling =true)] 
publicstaticexternbool SetWindowPos(HandleRef hWnd, HandleRef hWndInsertAfter, int x, int y, int cx, int cy, int flags); 
[DllImport("user32.dll")] 
publicstaticexternint ReleaseDC(IntPtr window, IntPtr handle); 
} 
} 

namespace ShowInDesk 
{ 
publicenum DesktopLayer 
{ 
Progman =0, 
SHELLDLL =1, 
FolderView =2 
} 
} 

internal class User32 
{ 
public const int SE_SHUTDOWN_PRIVILEGE =0x13; 
[DllImport("user32.dll")] 
public static extern IntPtr FindWindow(string lpClassName, string lpWindowName); 
[DllImport("user32.dll")] 
public static extern IntPtr SetParent(IntPtr hWndChild, IntPtr hWndNewParent); 
[DllImport("user32.dll")] 
public static externbool SetWindowPos(IntPtr hWnd, int hWndInsertAfter, int X, int Y, int cx, 
int cy, uint uFlags); 
} 

public MainForm()
{
InitializeComponent();
try
{
if (Environment.OSVersion.Version.Major <6)
{
base.SendToBack();
IntPtr hWndNewParent = User32.FindWindow("Progman", null);
User32.SetParent(base.Handle, hWndNewParent);
}
else
{
User32.SetWindowPos(base.Handle, 1, 0, 0, 0, 0, User32.SE_SHUTDOWN_PRIVILEGE);
}
}
catch (ApplicationException exx)
{
MessageBox.Show(this, exx.Message, "Pin to Desktop");
}
}
private void MainForm_Activated(object sender, EventArgs e)
{
if (Environment.OSVersion.Version.Major >=6)
{
User32.SetWindowPos(base.Handle, 1, 0, 0, 0, 0, User32.SE_SHUTDOWN_PRIVILEGE);
}
}
private void MainForm_Paint(object sender, PaintEventArgs e)
{
if (Environment.OSVersion.Version.Major >=6)
{
User32.SetWindowPos(base.Handle, 1, 0, 0, 0, 0, User32.SE_SHUTDOWN_PRIVILEGE);
}
}