<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <startup> 
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.6.1" />
    </startup>
<appSettings>
  <add key="SoftName" value="Sword7" />
  <add key="Supplier" value="SoftStar" />
  <add key="EnabledTcp" value="1" />
</appSettings>
<connectionStrings>
  <add name="DataConnect" providerName="MySql.Data" connectionString="server=127.0.0.1;Database=test;Uid=root;Pwd=root;" />
  <add name="ExternalConnect" providerName="System.Data.SqlClient" connectionString="server=127.0.0.1;Database=external;Uid=root;Pwd=123456;" />
</connectionStrings>
</configuration>

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Configuration;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace SaveDefaultXmlConfigDemo
{
    public partial class FormSaveDefaultXmlConfig : Form
    {
        public FormSaveDefaultXmlConfig()
        {
            InitializeComponent();
            //添加引用System.Configuration
        }
        private void btnSaveConfig_Click(object sender, EventArgs e)
        {
            try
            {
                Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
                List<Tuple<string, string>> tupleAppSettings = GetAppSettingList();
                for (int i = 0; i < tupleAppSettings.Count; i++)
                {
                    //修改配置節(jié)點(diǎn)AppSettings的內(nèi)容
                    config.AppSettings.Settings[tupleAppSettings[i].Item1].Value = tupleAppSettings[i].Item2;
                }
                List<Tuple<string, string, string>> tupleConnectionStrings = GetConnectionStringList();
                for (int i = 0; i < tupleConnectionStrings.Count; i++)
                {
                    //修改配置節(jié)點(diǎn)ConnectionStrings的內(nèi)容
                    config.ConnectionStrings.ConnectionStrings[tupleConnectionStrings[i].Item1].ProviderName = tupleConnectionStrings[i].Item2;
                    config.ConnectionStrings.ConnectionStrings[tupleConnectionStrings[i].Item1].ConnectionString = tupleConnectionStrings[i].Item3;
                }
                //保存配置文件
                config.Save();
                MessageBox.Show($"保存應(yīng)用程序配置文件成功，開始重新加載應(yīng)用程序配置.", "提示");
                //刷新配置
                FormSaveDefaultXmlConfig_Load(null, e);
            }
            catch (Exception ex)
            {
                MessageBox.Show($"保存應(yīng)用程序配置文件出錯(cuò):{ex.Message}", "出錯(cuò)");
            }
        }
        /// <summary>
        /// 獲取配置節(jié)點(diǎn)AppSettings的所有內(nèi)容，將其添加到元組列表中
        /// </summary>
        /// <returns></returns>
        private List<Tuple<string, string>> GetAppSettingList()
        {
            List<Tuple<string, string>> tupleAppSettings = new List<Tuple<string, string>>();
            for (int i = 0; i < groupBox1.Controls.Count; i++)
            {
                if (groupBox1.Controls[i] is Label lbl)
                {
                    Control[] controls = groupBox1.Controls.Find($"txtValue{lbl.Tag}", true);
                    if (controls == null || controls.Length == 0)
                    {
                        throw new Exception($"沒有找到【{lbl.Text}】對(duì)應(yīng)的文本框控件【txtValue{lbl.Tag}】");
                    }
                    tupleAppSettings.Add(Tuple.Create(lbl.Text, controls[0].Text));
                }
            }
            return tupleAppSettings;
        }
        /// <summary>
        /// 獲取配置節(jié)點(diǎn)onnectionStrings的所有內(nèi)容，將其添加到元組列表中
        /// </summary>
        /// <returns></returns>
        private List<Tuple<string, string, string>> GetConnectionStringList()
        {
            List<Tuple<string, string, string>> tupleConnectionStrings = new List<Tuple<string, string, string>>();
            for (int i = 0; i < groupBox2.Controls.Count; i++)
            {
                if (groupBox2.Controls[i] is Label lbl && lbl.Name.StartsWith("lblName"))
                {
                    Control[] controlProviderNames = groupBox2.Controls.Find($"txtProviderName{lbl.Tag}", true);
                    if (controlProviderNames == null || controlProviderNames.Length == 0)
                    {
                        throw new Exception($"沒有找到【{lbl.Text}】對(duì)應(yīng)的文本框控件【txtProviderName{lbl.Tag}】");
                    }
                    Control[] controlConnectionStrings = groupBox2.Controls.Find($"txtConnectionString{lbl.Tag}", true);
                    if (controlConnectionStrings == null || controlConnectionStrings.Length == 0)
                    {
                        throw new Exception($"沒有找到【{lbl.Text}】對(duì)應(yīng)的文本框控件【txtConnectionString{lbl.Tag}】");
                    }
                    tupleConnectionStrings.Add(Tuple.Create(lbl.Text, controlProviderNames[0].Text, controlConnectionStrings[0].Text));
                }
            }
            return tupleConnectionStrings;
        }
        private void FormSaveDefaultXmlConfig_Load(object sender, EventArgs e)
        {
            try
            {
                Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
                txtFilePath.Text = config.FilePath;
                //讀取配置AppSetting節(jié)點(diǎn),
                KeyValueConfigurationCollection keyValueCollection = config.AppSettings.Settings;
                AddAppSettingConfig(keyValueCollection);
                //讀取連接字符串ConnectionStrings節(jié)點(diǎn)
                ConnectionStringSettingsCollection connectionCollection = config.ConnectionStrings.ConnectionStrings;
                AddConnectionStringConfig(connectionCollection);
            }
            catch (Exception ex)
            {
                MessageBox.Show($"加載應(yīng)用程序配置文件出錯(cuò):{ex.Message}", "出錯(cuò)");
            }
        }
        /// <summary>
        /// 讀取所有的AppSetting節(jié)點(diǎn)，將其綁定到groupBox1中
        /// 只考慮在配置文件中【IsPresent為true】的節(jié)點(diǎn)
        /// </summary>
        /// <param name="keyValueCollection"></param>
        private void AddAppSettingConfig(KeyValueConfigurationCollection keyValueCollection)
        {
            groupBox1.Controls.Clear();
            int index = 0;
            foreach (KeyValueConfigurationElement keyValueElement in keyValueCollection)
            {
                ElementInformation elemInfo = keyValueElement.ElementInformation;
                if (!elemInfo.IsPresent)
                {
                    //考慮到部分配置不是在App.exe.config配置文件中，此時(shí)不做處理
                    continue;
                }
                Label label = new Label();
                label.AutoSize = true;
                label.Location = new System.Drawing.Point(20, 20 + index * 30);
                label.Name = $"lblKey{index + 1}";
                label.Text = keyValueElement.Key;
                label.Tag = index + 1;
                TextBox textBox = new TextBox();
                textBox.Location = new System.Drawing.Point(120, 20 + index * 30);
                textBox.Name = $"txtValue{index + 1}";
                textBox.Size = new System.Drawing.Size(300, 21);
                textBox.Text = keyValueElement.Value;
                groupBox1.Controls.AddRange(new Control[] { label, textBox });
                index++;
            }
        }
        /// <summary>
        /// 讀取所有的ConnectionString節(jié)點(diǎn)，將其綁定到groupBox2中
        /// 只考慮在配置文件中【IsPresent為true】的節(jié)點(diǎn)
        /// </summary>
        /// <param name="connectionCollection"></param>
        private void AddConnectionStringConfig(ConnectionStringSettingsCollection connectionCollection)
        {
            groupBox2.Controls.Clear();
            int index = 0;
            foreach (ConnectionStringSettings connectElement in connectionCollection)
            {
                ElementInformation elemInfo = connectElement.ElementInformation;
                if (!elemInfo.IsPresent)
                {
                    //考慮到連接字符串有系統(tǒng)默認(rèn)配置，不在配置文件中【IsPresent=false】，因此過濾掉,如下面兩個(gè)
                    //LocalSqlServer、LocalMySqlServer
                    continue;
                }
                Label label = new Label();
                label.AutoSize = true;
                label.Location = new System.Drawing.Point(20, 20 + index * 30);
                label.Name = $"lblName{index + 1}";
                label.Text = connectElement.Name;
                label.Tag = index + 1;
                TextBox textBox = new TextBox();
                textBox.Location = new System.Drawing.Point(120, 20 + index * 30);
                textBox.Name = $"txtConnectionString{index + 1}";
                textBox.Size = new System.Drawing.Size(360, 21);
                textBox.Text = connectElement.ConnectionString;
                Label lblFixed = new Label();
                lblFixed.AutoSize = true;
                lblFixed.Location = new System.Drawing.Point(500, 20 + index * 30);
                lblFixed.Name = $"lblFixed{index + 1}";
                lblFixed.Text = "提供程序名稱";
                TextBox txtProviderName = new TextBox();
                txtProviderName.Location = new System.Drawing.Point(580, 20 + index * 30);
                txtProviderName.Name = $"txtProviderName{index + 1}";
                txtProviderName.Size = new System.Drawing.Size(140, 21);
                txtProviderName.Text = connectElement.ProviderName;
                groupBox2.Controls.AddRange(new Control[] { label, textBox, lblFixed, txtProviderName });
                index++;
            }
        }
    }
}