How to register assembly using custom action in WIX toolset - custom-action

Question

My Wix toolset installer installs many files, but only one of these I would like to register for COM interop. I have tried the heat automatic registration but can't get it to work, so am falling back to what I used to do in installshield which is run a custom action at the end of installation to register using regasm.
This is failing for reasons I don't understand.
My Product.wxs file registers the action as follows:
<InstallExecuteSequence>
<Custom Action="RegisterAddIn" After="InstallFiles">NOT REMOVE</Custom>
</InstallExecuteSequence>
Then creates the action here:
<Fragment>
<CustomAction Id ="RegisterAddIn" Directory ="INSTALLFOLDER" Execute="immediate" ExeCommand="[WindowsFolder]Microsoft.NET\Framework\v4.0.30319\regasm /codebase /tlb "[INSTALLFOLDER]Aeolus.Excel.Addin.dll"" Return ="check"/>
</Fragment>
On running this installer I get the error
"A program run as part of setup did not finish as expected."
Extract from the msiexec log doesn't shown below.
CustomAction RegisterAddIn returned actual error code 100 (note this may not be 100% accurate if translation happened inside sandbox)
MSI (s) (54:38) [12:40:54:765]: Note: 1: 1722 2: RegisterAddIn 3: C:\Program Files (x86)\Aeolus\ 4: C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319\regasm /codebase /tlb "C:\Program Files (x86)\Aeolus\Aeolus.Excel.Addin.dll"
MSI (s) (54:38) [12:40:54:765]: Note: 1: 2205 2: 3: Error
MSI (s) (54:38) [12:40:54:765]: Note: 1: 2228 2: 3: Error 4: SELECT `Message` FROM `Error` WHERE `Error` = 1722
Error 1722. There is a problem with this Windows Installer package. A program run as part of the setup did not finish as expected. Contact your support personnel or package vendor. Action RegisterAddIn, location: C:\Program Files (x86)\Aeolus\, command: C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319\regasm /codebase /tlb "C:\Program Files (x86)\Aeolus\Aeolus.Excel.Addin.dll"
MSI (s) (54:38) [12:40:56:746]: Note: 1: 2205 2: 3: Error
MSI (s) (54:38) [12:40:56:746]: Note: 1: 2228 2: 3: Error 4: SELECT `Message` FROM `Error` WHERE `Error` = 1709
MSI (s) (54:38) [12:40:56:746]: Product: Aeolus -- Error 1722. There is a problem with this Windows Installer package. A program run as part of the setup did not finish as expected. Contact your support personnel or package vendor. Action RegisterAddIn, location: C:\Program Files (x86)\Aeolus\, command: C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319\regasm /codebase /tlb "C:\Program Files (x86)\Aeolus\Aeolus.Excel.Addin.dll"
Editing the .msi file with Orca, I have this entry in the table which looks correct to me:
[WindowsFolder]Microsoft.NET\Framework\v4.0.30319\regasm /codebase /tlb "[INSTALLFOLDER]Aeolus.Excel.Addin.dll"
If I remove these custom actions, run my installer, then run this in a command prompt (run as administrator):
%WINDIR%\Microsoft.NET\Framework\v4.0.30319\regasm /codebase /tlb "C:\Program Files (x86)\Aeolus\Aeolus.Excel.Addin.dll"
It registers fine. if not run as administrator it fails of course. Can I assume any custom actions will be run as administrator?

Answer 1

In case anyone else has similar issues, I managed to fix it. It turned out to be a permission issue. I was assuming that the installer and all custom actions ran as administrator but actually you have to tell it to run at that level of permission.
So I needed to make 3 fixes.
1. Request elevated permission in package definintion:
<Package InstallerVersion="200" Compressed="yes" InstallScope="perMachine" InstallPrivileges="elevated" AdminImage="yes"/>
Set "Execute" to "deferred" and "Impersonate" to "no" in custom action definition:
<CustomAction Id ="RegisterAddIn" Directory ="INSTALLFOLDER" Execute="deferred" ExeCommand="[WindowsFolder]Microsoft.NET\Framework\v4.0.30319\regasm /codebase /tlb "[INSTALLFOLDER]Aeolus.Excel.Addin.dll"" Return ="check" Impersonate="no"/>
Then it all runs as expected.