[wix-users] Can't Access CustomData during uninstall

[Justin Cox]

I have custom scripts to backup folders during an install, rollback, and
uninstall.  they all work except for the uninstall.
I set the value:
  <CustomAction Id="SetFolderValuesUninstall" Property="UninstallFolders"
Value="FolderList=[INSTALLCLIENTINTERFACEDIR]"/>

I execute the command:
  <CustomAction Id="UninstallFolders" BinaryKey="XXXXXShared.CA.dll"
DllEntry="UninstallFolders" Return="check" Execute="deferred" />

My C# code is:
        [CustomAction]
        public static ActionResult UninstallFolders(Session session)
        {
            ActionResult ar = ActionResult.Success;
            try
            {
                string folderlist = session.CustomActionData["FolderList"];
                MessageBox.Show("FolderList = " + folderlist);
                List<string> foldersToDelete =
folderlist.Split('|').ToList();
                ar = DeleteFolders(foldersToDelete, session);
                return ar;
            }
            catch (Exception ex)
            {
                ar = immediateErrorCatcher(ex, session);
                return ar;
            }
        }

Everything works fine during the install, but during the uninstall, it sets
the value correctly:

MSI (s) (60:04) [17:33:58:021]: PROPERTY CHANGE: Adding UninstallFolders
property. Its value is
'FolderList=C:\inetpub\wwwroot\XXXXXClientInterface\'.

Then, I get this error in verbose logging:
Calling custom action
XXXXXShared!XXXXXShared.DPWixExtension.UninstallFolders
Exception thrown by custom action:
System.Reflection.TargetInvocationException: Exception has been thrown by
the target of an invocation. --->
Microsoft.Deployment.WindowsInstaller.InstallerException: Cannot access
session details from a non-immediate custom action
   at Microsoft.Deployment.WindowsInstaller.Session.ValidateSessionAccess()
   at Microsoft.Deployment.WindowsInstaller.Session.set_Item(String
property, String value)
   at XXXXXShared.DPWixExtension.immediateErrorCatcher(Exception ex,
Session ses)
   at XXXXXShared.DPWixExtension.UninstallFolders(Session session)
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object
arguments, Signature sig, Boolean constructor)
   at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj,
Object parameters, Object arguments)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags
invokeAttr, Binder binder, Object parameters, CultureInfo culture)
   at
Microsoft.Deployment.WindowsInstaller.CustomActionProxy.InvokeCustomAction(Int32
sessionHandle, String entryPoint, IntPtr remotingDelegatePtr)
CustomAction UninstallFolders returned actual error code 1603 (note this
may not be 100% accurate if translation happened inside sandbox)


the error is happening when I hite "string folderlist =
session.CustomActionData["FolderList"];"

Is it possible to pass CustomActionData during an uninstall? Or has the
installer already thrown out those variables?