App.Config详解

String str = ConfigurationManager.AppSettings["DemoKey"];

Configuration cfa = 
　　ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
cfa.AppSettings.Settings["DemoKey"].Value = "DemoValue";
cfa.Save();

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

System.Configuration.ConfigurationSettings.AppSettings["Key"];

Configuration cfa = ConfigurationManager.
　　　　OpenExeConfiguration(ConfigurationUserLevel.None);
cfa.AppSettings.Settings.Add("key", "Name") ||　
　　cfa.AppSettings.Settings["BrowseDir"].Value = "name";

<?xmlversion="1.0"encoding="utf-8" ?>
<configuration>
</configuration>

<!--数据库连接串-->
     <connectionStrings>
         <clear />
         <addname="conJxcBook"
              connectionString="Data Source=localhost;Initial Catalog=jxcbook;User                                   ID=sa;password=********"
              providerName="System.Data.SqlClient" />
     </connectionStrings>

 <appSettings>
         <clear />
         <addkey="userName"value="" />
         <addkey="password"value="" />
         <addkey="Department"value="" />
         <addkey="returnValue"value="" />
         <addkey="pwdPattern"value="" />
         <addkey="userPattern"value="" />
</appSettings>

///<summary>
///依据连接串名字connectionName返回数据连接字符串
///</summary>
///<param name="connectionName"></param>
///<returns></returns>
private static string GetConnectionStringsConfig(string connectionName)
{
string connectionString =
        ConfigurationManager.ConnectionStrings[connectionName].ConnectionString.ToString();
    Console.WriteLine(connectionString);
    return connectionString;
}

///<summary>
///更新连接字符串
///</summary>
///<param name="newName">连接字符串名称</param>
///<param name="newConString">连接字符串内容</param>
///<param name="newProviderName">数据提供程序名称</param>
private static void UpdateConnectionStringsConfig(string newName,
    string newConString,
    string newProviderName)
{
    bool isModified = false;    //记录该连接串是否已经存在
    //如果要更改的连接串已经存在
    if (ConfigurationManager.ConnectionStrings[newName] != null)
    {
        isModified = true;
    }
    //新建一个连接字符串实例
    ConnectionStringSettings mySettings =
        new ConnectionStringSettings(newName, newConString, newProviderName);
    // 打开可执行的配置文件*.exe.config
    Configuration config =
        ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
    // 如果连接串已存在，首先删除它
    if (isModified)
    {
        config.ConnectionStrings.ConnectionStrings.Remove(newName);
    }
    // 将新的连接串添加到配置文件中.
    config.ConnectionStrings.ConnectionStrings.Add(mySettings);
    // 保存对配置文件所作的更改
    config.Save(ConfigurationSaveMode.Modified);
    // 强制重新载入配置文件的ConnectionStrings配置节
    ConfigurationManager.RefreshSection("ConnectionStrings");
}

///<summary>
///返回＊.exe.config文件中appSettings配置节的value项
///</summary>
///<param name="strKey"></param>
///<returns></returns>
private static string GetAppConfig(string strKey)
{
    foreach (string key in ConfigurationManager.AppSettings)
    {
        if (key == strKey)
        {
            return ConfigurationManager.AppSettings[strKey];
        }
    }
    return null;
}

///<summary>
///在＊.exe.config文件中appSettings配置节增加一对键、值对
///</summary>
///<param name="newKey"></param>
///<param name="newValue"></param>
private static void UpdateAppConfig(string newKey, string newValue)
{
    bool isModified = false;   
    foreach (string key in ConfigurationManager.AppSettings)
    {
       if(key==newKey)
        {   
            isModified = true;
        }
    }
 
    // Open App.Config of executable
    Configuration config =
        ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
    // You need to remove the old settings object before you can replace it
    if (isModified)
    {
        config.AppSettings.Settings.Remove(newKey);
    }   
    // Add an Application Setting.
    config.AppSettings.Settings.Add(newKey,newValue);  
    // Save the changes in App.config file.
    config.Save(ConfigurationSaveMode.Modified);
    // Force a reload of a changed section.
    ConfigurationManager.RefreshSection("appSettings");
}