C#如何提取經緯度檔案中的經緯度資料

//自定義類的函數
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Xml;
​
namespace FileConversion
{
    public class DataExtract
    {
        /// <summary>
        /// 對指定路徑的kml檔案，經緯度讀取，並返回經緯度集合MapConfig
        /// </summary>
        /// <param name="Path">檔案路徑名</param>
        /// <returns></returns>
        public List<String> MapConfigs(string filename)
        {
            List<String> mapConfigs = new List<String>();//範例化list集合
           
            string destPath = filename;//賦值檔案路徑
            if (destPath == null)//判斷路徑是否為空
            {
                MessageBox.Show("路徑為空");
                return null;
            }   
            XmlDocument xmldoc = new XmlDocument();
            try
            {
                xmldoc.Load(destPath);//載入kml檔案
                XmlElement root = xmldoc.DocumentElement;
                XmlNodeList xmlmark = root.GetElementsByTagName("coordinates");//獲取coordinates節點
                int i = 0;
                foreach (XmlNode xmlmarkNode in xmlmark)//遍歷所有coordinates節點
                {
                    if (xmlmarkNode.Name == "coordinates")
                    {
                        i++;
                        string mapConfig = "";//範例化
                        string str = xmlmarkNode.InnerText;//獲取節點的值
                        if (str.Equals("") || str.Contains(",") == false)
                        {
                            MessageBox.Show("第"+i.ToString()+"行資料有誤,將返回NULL值","錯誤");
                            return null;
                        }
                        string[] strings = str.Split(',');//對節點的值字串進行分割
                        mapConfig+= strings[0]+",";//經度值
                        mapConfig+= strings[1]+",";//緯度值
                        mapConfig+= strings[2];//
                        mapConfigs.Add(mapConfig);//新增在list中
                    }
                }
                return mapConfigs;
            }
            catch
            {
                MessageBox.Show("檔案載入失敗或coordinates節點資料獲取失敗", "錯誤");
                return null;//注：kml檔案如果使用wps或者word開啟會再執行本程式會報錯，文字開啟執行不會報錯
            }
            
        }
    }
}
​
​
//上面是我們需要呼叫的類
​​
//這個是我們介面設計呼叫的類
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
​
namespace FileConversion
{
    public partial class Form4 : Form
    {
        public Form4()
        {
            InitializeComponent();
        }
        public string KmlPath = "";
        private void button6_Click(object sender, EventArgs e)
        {
            OpenFileDialog openFile = new OpenFileDialog();
            openFile.Filter = "KML檔案(*.kml)|*.kml|所有檔案|*.*";
            if (openFile.ShowDialog() != DialogResult.OK)//開啟檔案是否點選了取消
                return;
            KmlPath = openFile.FileName;
            textBox1.Text = KmlPath;
        }
​
        private void button7_Click(object sender, EventArgs e)
        {
            DataExtract data = new DataExtract();//自定義的函數，複製kml檔案經緯度資料提取
            if (KmlPath.Equals("") == true)
            {
                MessageBox.Show("選擇檔案之後才能匯出");
            }
            else
            {
                if (checkBox1.Checked == true && checkBox2.Checked == false || checkBox1.Checked == true && checkBox2.Checked == true)
                {
                    List<string> list = data.MapConfigs(KmlPath);
                    string localFilePath = "";//檔案路徑
                    SaveFileDialog save = new SaveFileDialog();
                    save.Filter = "Txt（*.txt）|*.txt";        //設定檔案型別  
                    save.RestoreDirectory = true; //儲存對話方塊是否記憶上次開啟的目錄 
                    if (save.ShowDialog() == DialogResult.OK)//點了儲存按鈕進入 
                    {
                        localFilePath = save.FileName.ToString(); //獲得檔案路徑 
                        string fileName = localFilePath.Substring(localFilePath.LastIndexOf("") + 1); //獲取檔名，不帶路徑
                        //FileStream file = new FileStream(localFilePath, FileMode.Create);
                        foreach (string kml in list)
                        {
                            textBox2.Text += kml + "rn";
                            File.AppendAllText(localFilePath, kml + "rn");
                        }
​
                    }
                }
                else if (checkBox1.Checked == false && checkBox2.Checked == true)
                {
                    List<string> list = data.MapConfigs(KmlPath);
                    foreach (string kml in list)
                    {
                        textBox2.Text += kml + "rn";
                    }
                }
                else
                {
                    MessageBox.Show("選擇你需要的項");
                }
            }
        }
    }
}