Passing an absolute path to a custom action in WiX

I am using WiX to create an installer for my app

I have this snippet that describes the destination folder for my application:

  <Fragment>
    <Directory Id="TARGETDIR" Name="SourceDir">
      <Directory Id="CommonAppDataFolder">
        <Directory Id="Company" Name="myCompany">
          <Directory Id="App" Name="myProgram">
            <Directory Id="SQLGENERATORINSTALLFOLDER" Name="SqlLiteFolder" />
          </Directory>          
        </Directory>
      </Directory>
    </Directory>
  </Fragment>

      

        
        
        
      

    

I also have a custom action that requires a folder as an input parameter [App]

. If I pass [App]

to a custom action I would expect the entire folder path starting at C: \ all the way down to an internal folder

I would expect this:

C: \ ProgramData \ mycomp \ MyProgram \

Instead, I get this:

C: \ Windows \ Installer \ MSI971.tmp-C: \ ProgramData \ mycomp \ MyProgram \

It looks like WiX is adding a temporary folder of some kind

EDIT

This is how I pass the variable [App]

to the custom action:

  <CustomAction Id='GrantAccessToDatabase' BinaryKey='ActionLib' DllEntry='GrantAccess' Execute='deferred' Impersonate='no' />
  <Property Id="GrantAccessToDatabase" Value="DbFilePath=[App]" />

      

        
        
        
      

    

Please note that in order to pass a variable to a deferred custom action I need to use this syntax, it is explained here -> How to pass parameters to a custom action?

This is the C # part that gets the parameter:

[CustomAction]
public static ActionResult GrantAccess(Session session)
{
     var data = session.CustomActionData;
     var fullPath = data["DbFilePath"];
}

      

        
        
        
      

    

I would expect fullPath

:

C: \ ProgramData \ mycomp \ MyProgram \

Instead, I get:

C: \ Windows \ Installer \ MSI971.tmp-C: \ ProgramData \ mycomp \ MyProgram \