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.Threading;
namespace AppDemo
{
  public partial class frmMain : Form
  {
    public frmMain()
    {
      InitializeComponent();
    }
    /// <summary>
    /// 窗體初始狀態(tài)
    /// </summary>
    private FormWindowState fwsPrevious;
    /// <summary>
    /// 懸浮窗體
    /// </summary>
    private frmTopMost myTopMost;
    /// <summary>
    /// 主窗體的Load事件
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    private void frmMain_Load(object sender, EventArgs e)
    {
      fwsPrevious = this.WindowState;
      myTopMost = new frmTopMost(this);
    }
    /// <summary>
    /// 主窗體的SizeChanged事件
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    private void frmMain_SizeChanged(object sender, EventArgs e)
    {
      if (this.WindowState == FormWindowState.Minimized)
      {
        myTopMost.Show();
        this.ShowInTaskbar = false;
      }
      else if (this.WindowState != fwsPrevious)
      {
        fwsPrevious = this.WindowState;
      }
    }
    /// <summary>
    /// 還原窗口方法，即供懸浮窗口進行調用的。
    /// </summary>
    public void RestoreWindow()
    {
      this.WindowState = fwsPrevious;
      this.ShowInTaskbar = true;
    }
  }
}

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;
namespace AppDemo
{
  /// <summary>
  /// 首先要設置其窗體的FormBorderStyle為None，然后設置其的TopMost為true，接下來，就是主要是三個鼠標事件的處理
  /// </summary>
  public partial class frmTopMost : Form
  {
    public frmTopMost()
    {
      InitializeComponent();
    }
    /// <summary>
    /// 懸浮窗口的構造函數
    /// </summary>
    /// <param name="main"></param>
    public frmTopMost(frmMain main)
    {
      InitializeComponent();
      pParent = main;
    }
    private Point ptMouseCurrrnetPos, ptMouseNewPos, ptFormPos, ptFormNewPos;
    private bool blnMouseDown = false;
    private frmMain pParent;
    /// <summary>
    /// 懸浮窗口的Load事件
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    private void frmTopMost_Load(object sender, EventArgs e)
    {
      this.Show();
      this.Top = 100;
      this.Left = Screen.PrimaryScreen.Bounds.Width - 100;
      this.Width = 80;
      this.Height = 80;
    }
    private void frmTopMost_MouseMove(object sender, MouseEventArgs e)
    {
      if (blnMouseDown)
      {
        ptMouseNewPos = Control.MousePosition;
        ptFormNewPos.X = ptMouseNewPos.X - ptMouseCurrrnetPos.X + ptFormPos.X;
        ptFormNewPos.Y = ptMouseNewPos.Y - ptMouseCurrrnetPos.Y + ptFormPos.Y;
        Location = ptFormNewPos;
        ptFormPos = ptFormNewPos;
        ptMouseCurrrnetPos = ptMouseNewPos;
      }
    }
    private void frmTopMost_MouseDown(object sender, MouseEventArgs e)
    {
      if (e.Button == MouseButtons.Left)
      {
        blnMouseDown = true;
        ptMouseCurrrnetPos = Control.MousePosition;
        ptFormPos = Location;
      }
    }
    private void frmTopMost_MouseUp(object sender, MouseEventArgs e)
    {
      if (e.Button == MouseButtons.Left)
        blnMouseDown = false;
    }
    /// <summary>
    /// 雙擊懸浮窗體，進行恢復主窗體。
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    private void frmTopMost_MouseDoubleClick(object sender, MouseEventArgs e)
    {
      SwitchToMain();
    }
    private void SwitchToMain()
    {
      pParent.RestoreWindow();
      this.Hide();
    }
  }
}