c#创建子窗口时，子窗口无法获得焦点，总在父窗口控件的后面……

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using DevComponents.DotNetBar;

namespace TaskBarFloatWnd
{
public partial class TaskBarWnd : Office2007Form
{
public TaskBarWnd()
{
InitializeComponent();
actform = GetActiveWindow();
}
private bool isFristShow = true;//标识是否是首次加载
[System.Runtime.InteropServices.DllImport("user32.dll")]
public static extern IntPtr GetActiveWindow();//获得当前活动窗体
[System.Runtime.InteropServices.DllImport("user32.dll")]
public static extern IntPtr SetActiveWindow(IntPtr hwnd);//设置活动窗体

private IntPtr actform = IntPtr.Zero;//保存自己得到焦点前拥有活动窗体的柄
private void TaskBarWnd_Load(object sender, EventArgs e)
{
textBox1.Text = DateTime.Now + "——";
textBox1.Text = textBox1.Text + "目前正对网元1进行做单操作，10分钟内请大家避让";

}
protected override void OnActivated(EventArgs e)
{
base.OnActivated(e);
if (isFristShow == true)
{
SetActiveWindow(actform);
isFristShow = false;
}
}

private void TaskBarWnd_FormClosing(object sender, FormClosingEventArgs e)
{

}
}
}

private void button1_Click(object sender, EventArgs e)
{

TaskBarWnd taskWnd = new TaskBarWnd();
System.Drawing.Rectangle r = System.Windows.Forms.Screen.GetWorkingArea(taskWnd);
taskWnd.Location = new System.Drawing.Point(r.Right - taskWnd.Width, r.Bottom - taskWnd.Height);
taskWnd.Show();
}