/// <summary>
/// 左键、中键、右键单击判断
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void Form1_MouseClick(object sender, MouseEventArgs e)
{
    if (e.Button == MouseButtons.Left)
    {
        MessageBox.Show("左键单击");
    }
    else if (e.Button == MouseButtons.Middle)
    {
        MessageBox.Show("中键单击");
    }
    else if (e.Button == MouseButtons.Right)
    {
        MessageBox.Show("右键单击");
    }
}