c# 读写app.config

//AppConfigHelper.cs

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Xml;

namespace Utilities
{
public class AppConfigHelper
{
/// <summary>
/// 读取
/// </summary>
/// <param name="key"></param>
/// <returns></returns>
public static string GetValueByKey(string key)
{
return ConfigurationManager.AppSettings[key];
}

/// <summary>
/// 写入
/// </summary>
/// <param name="strKey"></param>
/// <param name="value"></param>
public static void ModifyAppSettings(string strKey, string value)
{
//value = ConstructionRealNameSystem.Utilities.CryptoHelper.EncryptAes(value);

var doc = new XmlDocument();
//获得配置文件的全路径
var strFileName = AppDomain.CurrentDomain.SetupInformation.ConfigurationFile;
doc.Load(strFileName);

var appSettingsNode = doc.SelectSingleNode("configuration//appSettings");

var nodes = appSettingsNode.ChildNodes;

//找出名称为“add”的所有元素
//var nodes = doc.GetElementsByTagName("add");
int i = 0;
for (; i < nodes.Count; i++)
{
//获得将当前元素的key属性
var xmlAttributeCollection = nodes[i].Attributes;
if (xmlAttributeCollection != null)
{
var att = xmlAttributeCollection["key"];
if (att == null) continue;
//根据元素的第一个属性来判断当前的元素是不是目标元素
if (att.Value != strKey) continue;
//对目标元素中的第二个属性赋值
att = xmlAttributeCollection["value"];
att.Value = value;
}
break;
}

//没有此节点，则新增
if (i >= nodes.Count)
{
XmlElement title = doc.CreateElement("add");
title.SetAttribute("key", strKey);
title.SetAttribute("value", value);
appSettingsNode.AppendChild(title);
}

//保存上面的修改
doc.Save(strFileName);
ConfigurationManager.RefreshSection("appSettings");
}
}
}

<!-- app.config -->

<?xml version="1.0" encoding="utf-8"?>
<configuration>
<appSettings>
<add key="key1" value="value1" />
</appSettings>
</configuration>