C#實現主窗體工具欄上按鈕兩幅圖片的交互效果

初次發文，敬請包涵。
using System.Runtime.InteropServices;
窗口類添加以下成員或函數
private static int buttonIndex;
[DllImport("User32", CharSet = CharSet.Auto)]
public static extern IntPtr SendMessage(IntPtr hWnd, uint msg, uint wParam, ref Point lParam);
public const int TB_HITTEST = 1093;
//本例為四個按鈕(注意：當添加屬性style為separator的按鈕後要作相應的變化)
//添加一個ImageList控件ImageList1(添加八個圖片依次為0...7，順序不能變，
//注意交互時圖片0，1，2，3分別對應圖片4，5，6，7)
//添加一個ToolBar控件ToolBar1(其ImageList屬性為ImageList1，
//四個按鈕的imageindex分別為0,1,2,3)

//工具欄MouseMove事件
private void toolBar1_MouseMove(object sender, System.Windows.Forms.MouseEventArgs e)
{
Point pt = new Point(e.X, e.Y);
IntPtr result =
SendMessage(this.toolBar1.Handle, TB_HITTEST, 0, ref pt);
buttonIndex = result.ToInt32();
const int lowBtnIndex = 0;
const int highBtnIndex =3;
if((buttonIndex >= lowBtnIndex ) && (buttonIndex <= highBtnIndex))
{
for(int u=0;u<4;u++)
{
if(u==buttonIndex)
this.toolBar1.Buttons[buttonIndex].ImageIndex=4+buttonIndex;
else
this.toolBar1.Buttons[u].ImageIndex=u;
}
}
else
{
for(int u=0;u<4;u++)
this.toolBar1.Buttons[u].ImageIndex=u;
}
}

//工具欄MouseLeave事件
private void toolBar1_MouseLeave(object sender, System.EventArgs e)
{
if((buttonIndex >= 0) && (buttonIndex <=3))
{
this.toolBar1.Buttons[buttonIndex].ImageIndex=buttonIndex;
}
buttonIndex=4;
}