using?System;
using?System.Collections.Generic;
using?System.ComponentModel;
using?System.Data;
using?System.Drawing;
using?System.Linq;
using?System.Text;
using?System.Threading.Tasks;
using?System.Windows.Forms;

namespace?DrawPolygon
{
????public?partial?class?Form1?:?Form
????{
????????public?Form1（）
????????{
????????????InitializeComponent（）;
????????????Setstyle（Controlstyles.UserPaint?true）;
????????????Setstyle（Controlstyles.AllPaintingInWmPaint?true）;?//?禁止擦除背景.??
????????????Setstyle（Controlstyles.DoubleBuffer?true）;?//?雙緩沖
????????}

????????List?ListPolyon?=?new?List（）;
????????List?_tempPolyon?=?new?List（）;
????????Point?_tempPoint?=?new?Point（）;
????????bool?IsDrawPolyonstart?=?false;

????????bool?IsEdit?=?false;
????????int?SelectListIndex?=?0;
????????int?SelectRc?=?0;
????????public?float?isLeft1（Point?P0?Point?P1?Point?P2）
????????{
????????????float?abc?=?（（P1.X?-?P0.X）?*?（P2.Y?-?P0.Y）?-?（P2.X?-?P0.X）?*?（P1.Y?-?P0.Y））;
????????????return?abc;

????????}
????????private?bool?PointInFences（Point?pnt1?Point[]?fencePnts）
????????{

????????????int?wn?=?0?j?=?0;?//wn?計數器?j第二個點指針
????????????for?（int?i?=?0;?i?????????????{//開始循環
????????????????if?（i?==?fencePnts.Length?-?1）
????????????????????j?=?0;//如果?循環到最后一點?第二個指針指向第一點
????????????????else
????????????????????j?=?j?+?1;?//如果不是?，則找下一點


????????????????if?（fencePnts[i].Y?<=?pnt1.Y）?//?如果多邊形的點?小于等于?選定點的?Y?坐標
????????????????{
????????????????????if?（fencePnts[j].Y?>?pnt1.Y）?//?如果多邊形的下一點?大于于?選定點的?Y?坐標
????????????????????{
????????????????????????if?（isLeft1（fencePnts[i]?fencePnts[j]?pnt1）?>?0）
????????????????????????{
????????????????????????????wn++;
????????????????????????}
????????????????????}
????????????????}
????????????????else
????????????????{
????????????????????if?（fencePnts[j].Y?<=?pnt1.Y）
????????????????????{
????????????????????????if?（isLeft1（fencePnts[i]?fencePnts[j]?pnt1）?????????????????????????{
????????????????????????????wn--;
????????????????????????}
????????????????????}
????????????????}
????????????}
????????????if?（wn?==?0）
????????????????return?false;
????????????else
????????????????return?true;
????????}
????????private?void?pictureBox1_MouseDoubleClick（object?sender?MouseEventArgs?e）
????????{
????????????if?（!IsDrawPolyonstart）
????????????{
????????????????if?（_tempPolyon.Count?<=?2）
????????????????{
????????????????????MessageBox.Show（“多邊形至少三個點“）;
????????????????????return;
????????????????}
????????????????IsDrawPolyonstart?=?true;
????????????????_tempPolyon.Add（new?Point（e.X?e.Y））;

????????????????_tempPolyon.Add（_tempPolyon[0]）;


????????????????ListPolyon.Add（_tempPolyon.ToArray（））;





????????????????_tempPolyon?=?new?List（）;
????????????}
????????????if?（IsDrawPolyonstart?&&?e.Button?==?MouseButtons.Right）
????????????{

????????????????for?（int?i?=