.NET button的SendToBack()方法

public partial class control : UserControl
{
public control()
{
InitializeComponent();
this.button1.Click +=new EventHandler (bt1_click);
this.button2.Click += new EventHandler(bt2_click);
this.button3.Click += new EventHandler(bt3_click);
this.button4.Click += new EventHandler(bt4_click);
this.button5.Click += new EventHandler(bt5_click);
button3.Dock = DockStyle.Bottom;
button4.Dock = DockStyle.Bottom;
button5.Dock = DockStyle.Bottom;
button2.Dock = DockStyle.Bottom;

button2.SendToBack();
button3.SendToBack();
button4.SendToBack();
button5.SendToBack();

}
private void bt1_click(object sender,EventArgs args)
{
button1.Dock = DockStyle.Top;
button2.Dock = DockStyle.Bottom;
button3.Dock = DockStyle.Bottom;
button4.Dock = DockStyle.Bottom;
button5.Dock = DockStyle.Bottom;
button3.SendToBack();//及在当下的控件列表里，它放在最上边，当然要知道执行顺序是重上往下的。
button4.SendToBack();
button5.SendToBack();
}
private void bt2_click(object sender, EventArgs args)
{
button1.Dock = DockStyle.Top;
button1.SendToBack();
button2.Dock = DockStyle.Top;
button3.Dock = DockStyle.Bottom;
button4.Dock = DockStyle.Bottom;
button5.Dock = DockStyle.Bottom;
button4.SendToBack();
button5.SendToBack();
}
private void bt3_click(object sender, EventArgs args)
{
button1.Dock = DockStyle.Top;
button2.Dock = DockStyle.Top;
button3.Dock = DockStyle.Top;
button2.SendToBack();
button1.SendToBack();
button4.Dock = DockStyle.Bottom;
button5.Dock = DockStyle.Bottom;
button5.SendToBack();

}
private void bt4_click(object sender, EventArgs args)
{
button1.Dock = DockStyle.Top;
button2.Dock = DockStyle.Top;
button3.Dock = DockStyle.Top;
button3.SendToBack();
button2.SendToBack();
button1.SendToBack();
button4.Dock = DockStyle.Top;
button5.Dock = DockStyle.Bottom;
}
private void bt5_click(object sender, EventArgs args)
{
button1.Dock = DockStyle.Top;
button2.Dock = DockStyle.Top;
button3.Dock = DockStyle.Top;
button4.Dock = DockStyle.Top;
button5.Dock = DockStyle.Top;

button5.SendToBack();
button4.SendToBack();
button3.SendToBack();
button2.SendToBack();
button1.SendToBack();

}
}