title: Write to XML file in maintenance mode with Wix
body: <p>I'm using Wix 3.10. I've got an installer that asks the user to enter a value when they install, which it saves in an XML file. This was done with XmlFile, as part of the component which installs the XML file, and this works fine. However now I want to be able to go to add/remove programs, click the Change button, so the installer is run in maintenance mode, the user can change the value they previously entered, and it will update the XML file, however I'm not sure how to do this, it doesn't work as it is being set in the component. Any pointers would be appreciated, thanks! Below is the component xml, SETTING is the property set from the UI text box which gets written to the XML file:</p>
  
  <pre><code>&lt;Component Id="MyApp.exe.config" Directory="INSTALLFOLDER" Guid="my-guid"&gt;
    &lt;RegistryKey Root="HKMU" Key="Software\MyCompany\MyApp"&gt;
      &lt;RegistryValue Name="MyApp.exe.config" Value="1" KeyPath="yes" Type="integer"/&gt;
    &lt;/RegistryKey&gt;
    &lt;File Source="MyApp.exe.config"/&gt;
    &lt;util:XmlFile Id="Config1" File="[INSTALLFOLDER]MyApp.exe.config" Action="setValue" Name="value" Value="[SETTING]" ElementPath="//configuration//appSettings//add" Sequence="1"/&gt;
  &lt;/Component&gt;
  </code></pre>