在winform中用以下方法修改WindowsFormsApplication5.exe.config后
 var config = ConfigurationManager.OpenExeConfiguration(@"D:\Users\Administrator\documents\visual studio 2013\Projects\WindowsFormsApplication5\WindowsFormsApplication5\bin\Debug\" + "WindowsFormsApplication5.exe");
            AppSettingsSection appSection = (AppSettingsSection)config.GetSection("appSettings");
            appSection.Settings["Pwd"].Value = "test";
            config.Save(ConfigurationSaveMode.Modified);

修改前xml

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <startup>
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
    </startup>
  <appSettings>
    <!-- 你好 -->
    <add key="Pwd" value="yms6666" />
  </appSettings>
</configuration>

修改后

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <startup>
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
    </startup>
  <appSettings>
    <add key="Pwd" value="test" />
  </appSettings>
</configuration>

值是修改成功了，可是注释没了。。。