app.config中增加appSettings节点，conn.open时报初始化错误

在app.config中增加appSettings节点后，运行到conn.open时报如下错误：

    “System.Transactions.Diagnostics.DiagnosticTrace”的类型初始值设定项引发异常。”

将configSections节点放到configuration下的第一元素后问题解决，原因未知。

app.config改动前：

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <appSettings>
        <add key="busCity" value="上海,东莞,中山,丽水,乐山,佛山,保定,北海,南京,南充,南宁,南通,台州,合肥,唐山,安阳,宜宾,巴中,常州,常德,广元,广 州,德阳,惠州,成都,扬州,攀枝花,昆明,昭通,杭州,汕头,江门,泰州,泸州,淮安,深圳,清远,烟台,玉林,珠海,苏州,衢州,达州,遂宁,郑州, 重庆,镇江,长沙,阳江,雅安,青岛,韶关"/>
        <add key="busId" value="398328,595874,662326,280787,352434,601492,357595,355542,293437,390110,354921,489828,280796,390186,622586,338884,352959,347956,283053,376904,351940,662530,351110,662499,348289,690040,390582,609990,621734,277073,673785,666466,327372,354010,282585,635260,666754,398034,357334,556102,611718,281511,352419,351093,347918,399907,419461,359516,655530,351904,397721,674569"/>
    </appSettings>

    <configSections>
        <sectionGroup name="userSettings" type="System.Configuration.UserSettingsGroup, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" >
            <section name="TrainTickets.Properties.Settings" type="System.Configuration.ClientSettingsSection, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" allowExeDefinition="MachineToLocalUser" requirePermission="false" />
        </sectionGroup>
    </configSections>
   
</configuration>

app.config改动后：

<?xml version="1.0" encoding="utf-8" ?>
<configuration>

      <configSections>
        <sectionGroup name="userSettings" type="System.Configuration.UserSettingsGroup, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" >
            <section name="TrainTickets.Properties.Settings" type="System.Configuration.ClientSettingsSection, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" allowExeDefinition="MachineToLocalUser" requirePermission="false" />
        </sectionGroup>
    </configSections>    <appSettings>
        <add key="busCity" value="上海,东莞,中山,丽水,乐山,佛山,保定,北海,南京,南充,南宁,南通,台州,合肥,唐山,安阳,宜宾,巴中,常州,常德,广元,广 州,德阳,惠州,成都,扬州,攀枝花,昆明,昭通,杭州,汕头,江门,泰州,泸州,淮安,深圳,清远,烟台,玉林,珠海,苏州,衢州,达州,遂宁,郑州, 重庆,镇江,长沙,阳江,雅安,青岛,韶关"/>
        <add key="busId" value="398328,595874,662326,280787,352434,601492,357595,355542,293437,390110,354921,489828,280796,390186,622586,338884,352959,347956,283053,376904,351940,662530,351110,662499,348289,690040,390582,609990,621734,277073,673785,666466,327372,354010,282585,635260,666754,398034,357334,556102,611718,281511,352419,351093,347918,399907,419461,359516,655530,351904,397721,674569"/>
    </appSettings>

   
   
</configuration>