App.config应用

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
	<appSettings>
		<add key="Email" value="admin@admin.com"/>
		<add key="Password" value="123456"/>
		<add key="SmtpServer" value="smtp.admin.com"/>
	</appSettings>
</configuration>

using System.Configuration;
using System.Windows;

namespace WpfApp3
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void buttonOpen_Click(object sender, RoutedEventArgs e)
        {
            var appSettings = ConfigurationManager.AppSettings;
            txtEmail.Text = appSettings["Email"]?.ToString();//根据Key读取<add>元素的Value
            txtPassword.Text = appSettings["Password"]?.ToString();//根据Key读取<add>元素的Value
            txtSmtp.Text = appSettings["SmtpServer"]?.ToString();//根据Key读取<add>元素的Value
        }

        private void buttonUpdate_Click(object sender, RoutedEventArgs e)
        {
            var config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
            config.AppSettings.Settings["Email"].Value = txtEmail.Text;//写入<add>元素的Value
            config.AppSettings.Settings["Password"].Value = txtPassword.Text;//写入<add>元素的Value
            config.AppSettings.Settings["SmtpServer"].Value = txtSmtp.Text;//写入<add>元素的Value
            config.AppSettings.Settings.Add("url", "http://www.google.com");//增加<add>元素
            config.AppSettings.Settings.Remove("name");//删除<add>元素
            config.AppSettings.SectionInformation.ForceSave = true;//保存文件
            config.Save(ConfigurationSaveMode.Modified);//一定要记得保存，写不带参数的config.Save()也可以
            //重新加载改变的节点
            ConfigurationManager.RefreshSection("appSettings");//刷新，否则程序读取的还是之前的值（可能已装入内存）
        }
    }
}

using System;
using System.Configuration;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            ReadAllSettings();
            ReadSetting("Setting1");
            ReadSetting("NotValid");
            AddUpdateAppSettings("NewSetting", "May 7, 2014");
            AddUpdateAppSettings("Setting1", "May 8, 2014");
            ReadAllSettings();
        }

        static void ReadAllSettings()
        {
            try
            {
                var appSettings = ConfigurationManager.AppSettings;

                if (appSettings.Count == 0)
                {
                    Console.WriteLine("AppSettings is empty.");
                }
                else
                {
                    foreach (var key in appSettings.AllKeys)
                    {
                        Console.WriteLine("Key: {0} Value: {1}", key, appSettings[key]);
                    }
                }
            }
            catch (ConfigurationErrorsException)
            {
                Console.WriteLine("Error reading app settings");
            }
        }

        static void ReadSetting(string key)
        {
            try
            {
                var appSettings = ConfigurationManager.AppSettings;
                string result = appSettings[key] ?? "Not Found";
                Console.WriteLine(result);
            }
            catch (ConfigurationErrorsException)
            {
                Console.WriteLine("Error reading app settings");
            }
        }

        static void AddUpdateAppSettings(string key, string value)
        {
            try
            {
                var configFile = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
                var settings = configFile.AppSettings.Settings;
                if (settings[key] == null)
                {
                    settings.Add(key, value);
                }
                else
                {
                    settings[key].Value = value;
                }
                configFile.Save(ConfigurationSaveMode.Modified);
                ConfigurationManager.RefreshSection(configFile.AppSettings.SectionInformation.Name);
            }
            catch (ConfigurationErrorsException)
            {
                Console.WriteLine("Error writing app settings");
            }
        }
    }
}