为什么修改我的app.config不起作用？

Question

这是我的AppConfig文件

[ { name: 'John',
    numberOfPets: 5,
    pets: [ 'petOne', 'petTwo', 'petThree' ] },
  { name: 'John', numberOfPets: 5, pets: [ 'petFour', 'petFive' ] },
  { name: 'Andrew',
    numberOfPets: 5,
    pets: [ 'petSix', 'petSeven', 'petEight' ] },
  { name: 'Andrew',
    numberOfPets: 5,
    pets: [ 'petNine', 'petTen' ] } ]

我想更改MainPrinter的名称

以下是我要做的事情：

<?xml version="1.0" encoding="utf-8"?>
<configuration>
    <startup> 
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5"/>
    </startup>
  <connectionStrings>
    <add name="Connection" connectionString="(local)\SQLexpress"/>
    <add name="MainPrinter" connectionString=""/>
  </connectionStrings>

</configuration>

但我不接受任何结果