WIX Writing user data into config file - wix

Question

I would like to ask a WiX installer question. I created a working installer that does many things already. I still need to ask the user for some specific information (the GUI is already done), and write it into a config file.
From this snippet, I think I could use the INSTALLFOLDER global variable.
<Directory Id="TARGETDIR" Name="SourceDir">
<Directory Id="IISROOT" Name='WebDir'>
<Directory Id="INSTALLFOLDER" Name="IVRDesigner">
</Directory>
</Directory>
</Directory>
This is the part, when I want to use that. This code is taken from a tutorial, should work well, if the source tag is filled properly. The ..\src\Web.config is just a dummy, so the code can compile. The default installed path for the web.config file will be C:\inetpub\wwwroot\myfolder, but the user can change this during the installation.
The question is: how could I use the global variable here, or what kind of solution, do you recommend?
Thanks in advance.
<Component Id="ConfigureWebConfig" Guid="*">
<File Id="Web.config" Name="MyConfigfile" Vital="yes" KeyPath="yes"
Source="..\src\Web.config" />
<util:XmlFile Id="AppConfigSetConnStr" Action="setValue"
Permanent="yes" File="[#Web.config]"
ElementPath="/configuration/connectionStrings/add[\[]#name='GeoIVRDesignerEntities'[\]]" Name="connectionString"
Value="data source=[DBSERVER];" />
</Component>

Answer 1

Under the Product tag I would add the properties that I want to be able to change in the config file like this:
<Property Id="BUILDRAN" Value="INSTALLER"/>
<Property Id="EMAIL_RECEIPIANT" Value="thisisnotme#notthere.com" />
Create the Fragment for the Directory Structure
<Fragment>
<Directory Id="TARGETDIR" Name="SourceDir" >
<Directory Id="BasicDir" Name="Dev_Home">
<Directory Id="BasicDirSuite" Name="TEST">
<Directory Id="INSTALLFOLDER" Name="DesignPatterns" />
</Directory>
</Directory>
</Directory>
</Fragment>
Declare another Fragment for the transformation of the config file
<util:XmlFile Id="AppConfigSetBuildRan" Action="setValue" Permanent="yes" File="[#App.config]"
ElementPath="/configuration/applicationSettings/MyApp.Properties.Settings/setting[\[]#name='BuildRan'[\]]/value"
Value="[BUILDRAN]" />
<util:XmlFile Id="AppConfigSetEmail" Action="setValue" Permanent="yes" File="[#App.config]"
ElementPath="/configuration/applicationSettings/MyApp.Properties.Settings/setting[\[]#name='TestValue'[\]]/value"
Value="[EMAIL_RECEIPIANT]" />
If you want you can create your own custom dialog to let the End user enter values for the properties [BUILDRAN] && [EMAIL_RECEIPIANT], or you could use the command line and set the properties with parameters
msiexec /i My.msi BUILDRAN=SuperDebug EMAIL_RECEIPIANT=you#home.com