private void ButtonGetAt_Click(Object sender, EventArgs e)
{
    ////实例化一个捕捉设置类对象setting，并设置相应属性
    SnapSetting setting = new SnapSetting();
    setting.FixedLength = 3000.0;
    setting.Tolerance = 20;
    setting.FixedAngle = 360;
    setting.IsSnappedLineBroken = true;
    setting.MaxSnappedCount = 520;
    setting.MinSnappedLength = 22;
    setting[SnapMode.PointOnLine] = true;

    //返回给定索引值的捕捉模式
    Int32 index = 0;
    SnapMode actual = setting.GetAt(index);

}