1 <?xml version="1.0" encoding="utf-8" ?>
2 <configuration>
3 </configuration>

1   <connectionStrings>
2     <clear/>
3     <add name="connect" connectionString="Data Source=localhost;Initial Catalog=test;User ID=sa;password=********"/>
4   </connectionStrings>

1   <appSettings>
2     <add key="DownloadPath" value="" />
3     <add key="ClientSettingsProvider.ServiceUri" value="" />
4   </appSettings>

 1 ///<summary>
 2 ///依据连接串名字connectionName返回数据连接字符串
 3 ///</summary>
 4 ///<param name="connectionName">连接串名字</param>
 5 ///<returns></returns>
 6 private static string GetConnectionStringsConfig(string connectionName)
 7 {
 8     string connectionString = 
 9         ConfigurationManager.ConnectionStrings[connectionName].ConnectionString.ToString();
10     return connectionString;
11 }

 1 ///<summary>
 2 ///更新连接字符串
 3 ///</summary>
 4 ///<param name="newName">连接字符串名称</param>
 5 ///<param name="newConString">连接字符串内容</param>
 6 ///<param name="newProviderName">数据提供程序名称</param>
 7 private static void UpdateConnectionStringsConfig(string newName,
 8     string newConString,
 9     string newProviderName)
10 {
11     bool isModified = false;    //记录该连接串是否已经存在
12     //如果要更改的连接串已经存在
13     if (ConfigurationManager.ConnectionStrings[newName] != null)
14     {
15         isModified = true;
16     }
17     //新建一个连接字符串实例
18     ConnectionStringSettings mySettings = 
19         new ConnectionStringSettings(newName, newConString, newProviderName);
20     // 打开可执行的配置文件*.exe.config
21     Configuration config = 
22         ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
23     // 如果连接串已存在，首先删除它
24     if (isModified)
25     {
26         config.ConnectionStrings.ConnectionStrings.Remove(newName);
27     }
28     // 将新的连接串添加到配置文件中.
29     config.ConnectionStrings.ConnectionStrings.Add(mySettings);
30     // 保存对配置文件所作的更改
31     config.Save(ConfigurationSaveMode.Modified);
32     // 强制重新载入配置文件的ConnectionStrings配置节
33     ConfigurationManager.RefreshSection("ConnectionStrings");
34 }

///<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");
}