WiX installer can't open config file

Question

I have a WPF application and I've created an MSI to install it with the WixToolset 3.11 and Visual Studio Extension 2019. I'm trying to add either XmlFile or XmlConfig item to change values in the config file. I'm getting the following error:

Failed to open XML file C:\Program Files(x86)\CO Apps\Main App\OurApp.exe.config. system error: -2147024786

The file path is the full filepath because I gave it the full path trying to resolve the issue. Here's the important parts of the wxs file

<Wix xmlns="http://schemas.microsoft.com/wix/2006/wi" 
        xmlns:wixutil="http://schemas.microsoft.com/wix/UtilExtension">
<Product Id="9E76F000-5525-4BDF-8262-AE46B035D9CE"
            Name="Our App"
            Language="1033"
            Version="2.0.0.0"
            Manufacturer="CO Apps"
            UpgradeCode="7CFB1B51-F5D5-4AD4-A509-F5C9BC05F875">
<Package Id="*" InstallerVersion="200" Compressed="yes" InstallScope="perMachine" Description="Our production application." />
<Directory Id="ProgramFilesFolder">
    <Directory Id="VTAPPSDIR" Name="CO Apps">
      <Directory Id="INSTALLFOLDER" Name="Our App">
        <Component Id="MainExecutable" Guid="748368D7-7581-4809-A8FE-DFB1093D6A02">
          <File Id="MainFile" Name="$(var.OurApp.TargetFileName)" DiskId="1" Source="$(var.OurApp.TargetDir)OurApp.exe" KeyPath="yes"></File>
          <File Id="OurApp.exe.config" ReadOnly="no" Source="$(var.OurApp.TargetDir)OurApp.exe.config"></File>
  ... More File items for DLLs

          <wixutil:XmlFile Id="SetAppMode" Action="setValue" File="C:\Program Files (x86)\CO Apps\Our App\OurApp.exe.confg" ElementPath="configuration/userSettings/OurApp.Properties.Settings/setting/AppMode/value" Value="Main" />
        </Directory>
    </Directory>
</Directory>

So I'm trying to set the "AppMode" value to "Main" when this installs. What I'm trying to set isn't the point it's that it can't seem to find or open the file. I've tried putting the XmlFile in its own component. I've tried several variations of File paths including [INSTALLDIR] and [INSTALLLOCATION] and the filename by itself. Without that line everything works great. With that line in, I get the error and it rolls back the install. I also tried XmlConfig instead of XmlFile:

<wixutil:XmlConfig Id="ClearConfigAppMode" Action="delete" File="[INSTALLLOCATION]OurApp.exe.config" ElementPath="userSettings/OurApp.Properties.Settings" Name="AppMode" />
  <wixutil:XmlConfig Id="SetAppMode" Action="create" File="[INSTALLLOCATION]OurApp.exe.config" ElementPath="userSettings/OurApp.Properties.Settings" On="install" Node="element">
<wixutil:XmlConfig Id="SetConfigAppModeName" ElementId="SetAppMode" File="[INSTALLLOCATION]OurApp.exe.config" Name="name" Value="AppMode" />
<wixutil:XmlConfig Id="SetConfigAppModeSerializeAs" ElementId="SetAppMode" File="[INSTALLLOCATION]OurApp.exe.config" Name="serializeAs" Value="String" />
  </wixutil:XmlConfig>
  <wixutil:XmlConfig Id="SetAppModeValue" Action="create" File="[INSTALLLOCATION]OurApp.exe.config" ElementPath="userSettings/OurApp.Properties.Settings" On="install" Node="element" Sequence="2">
<wixutil:XmlConfig Id="SetAppModeVAlueMain" ElementId="SetAppModeValue" File="[INSTALLLOCATION]OurApp.exe.config" Name="Value" Value="Main" />
  </wixutil:XmlConfig>

Since XmlConfig doesn't have setValue on an existing element I used the delete action to remove the item for use in development and insert a new one. Same error. It happens logged on as myself or as Administrator. Does anyone have a working example of WiX with WPF creating a MSI? I'm not looking for something as complex as WixBA. I just need to modify the app.exe.config file on install.

Thanks, Mike

Answer 1

Example: Though I rarely use this feature, I have this working example here (my test project for XML): https://github.com/glytzhkof/WiXUpdateXmlFile. Snippets of the sample here and here.

Disclaimer: I am not sure if follows best practice for XML updates, since I prefer to do XML updates from application launch code instead - if possible (single source, easier debugability and in general more familiar territory for most developers).

app.config/web.config appsettings: Maybe check out this answer regarding appsettings or this answer (looks better) - just for your review, not necessarily a suggestion. Keeping deployed files read-only helps a lot to overwrite them reliably during updates and the file you generate can be kept untouched by the installer (the file is de-coupled from installer - it never touches them). Or as I wrote: HKCU can also be used to write "the few settings you actually have to change". Not so nice conceptually?

Clouded Settings: Personally I think settings should never be file-based but clouded in our day and age (kept in a remote database). See section 6 and 7 here. How realistic this is for your application I don't know. New challenges and problems - no doubt (network issues, firewalls, launch problems, etc...), but benefits: versioned settings, recovery and management (enforce new settings). Not sure about all the practicalities - never been involved that much, but would love to get rid of settings files - especially for corporate apps. However, sometimes nice concepts don't meet reality well - maybe it is too involved?