button1.TabStop = false;button1.FlatAppearance.BorderSize = 0;
button1.FlatAppearance.BorderColor = Color.FromArgb(0, 255, 255, 255); //設置邊框的顏色Transparent
button1.FlatAppearance.MouseOverBackColor = Color.FromArgb(0, 255, 255, 255); //設置鼠標經過時候的背景顏色Transparent
button1.FlatAppearance.MouseDownBackColor = Color.FromArgb(0, 255, 255, 255); //設置鼠標按下時候的背景顏色Transparent

//鼠標落下設置一張圖片
private void button1_MouseDown(object sender, MouseEventArgs e)
{
     this.button1.Image = Image.FromFile(@"../../images/close_click.png");
}

//鼠標彈起恢復原來圖片
private void button1_MouseUp(object sender, MouseEventArgs e)
{
     this.button1.Image = Image.FromFile(@"../../images/close_default.png");
}

//響應點擊事件
private void button1_Click(object sender, EventArgs e)
{
     MessageBox.Show("I'm normal button");
}

private void pictureBox2_MouseDown(object sender, MouseEventArgs e)
 {
      this.pictureBox2.Image = Image.FromFile(@"../../images/close_click.png");
}

private void pictureBox2_MouseUp(object sender, MouseEventArgs e)
{
     this.pictureBox2.Image = Image.FromFile(@"../../images/close_default.png");
}

private void pictureBox2_Click(object sender, EventArgs e)
{
      MessageBox.Show("I'm closed");
}