The following “discussion” got a little out of hand. But I will leave it here as an explanation for people who research differences experienced between silent mode and interactive mode installs.
Yes, the short answer is that you can indeed see different installation or uninstallation behavior depending on how you invoke the (un)install.
This has mostly to do with how an MSI can run with different user interface levels, and this causes the entire user interface sequence (InstallUISequence) in the MSI to either be run or skipped entirely (silent installation). Once skipped, all custom actions defined only in the InstallUISequence will not run at all. If the MSI is well-designed, this is not a problem since user interface custom actions run in immediate mode and should never make changes to the system – they should just inquire for user data and settings, system state or help the user enter proper data for the installation. If the MSI is not well designed and changes are made to the system in the user interface, the installation will be incomplete when running in silent mode. This is a serious MSI design error which becomes all the more serious when you realized that all major corporations deploy software silently. I have seen such errors many times when doing corporate application repackaging. It is not a vote of confidence for the software, no matter how good it is. Weird and unpredictable problems are bound to surface.
Accordingly, the InstallExecuteSequence (which is the only one that runs when the setup is installed silently) should have all required custom actions that make system changes inserted there for an MSI to be correctly designed. As already stated, custom actions existing only in the user interface sequence should deal with getting values and settings from the user, whereas these values should be set and defined by command line or defined in transforms for a silent install.
Certain odd and erroneous combinations of custom action conditions can also cause differences between interactive and silent installs in special circumstances. And finally putting custom actions after InstallFinalize in the InstallExecuteSequence can cause actions to fail when run silently. There are certainly other potential problems as well.
In summary, if you do see a difference in installation behavior based on the user interface level, your MSI contains a serious design-flaw. You should always ensure that your MSI can be run silently with the equivalent result as interactively. And as already stated large corporations never run installations interactively since they push out software via software management systems such as SCCM.
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There are 4 MSI UI levels ranging from fully silent to fully interactive:
- INSTALLUILEVEL_NONE = 2, (totally silent)
- INSTALLUILEVEL_BASIC = 3, (progress bars and simple error handling)
- INSTALLUILEVEL_REDUCED = 4, (authored UI, no wizards)
- INSTALLUILEVEL_FULL = 5 (full UI)
- The important point is that for UILevel 2 and 3 the InstallUISequence is skipped.
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There is an MSI property UILevel holding the GUI level value 2, 3, 4 or 5. Check this property if your custom action must take the user interface type into account. This is obviously most important for totally silent installs that should never show any dialogs.
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When you right click an MSI and select uninstall you are generally running UILevel 3 (Basic UI with progress bar). This means the InstallUISequence is skipped.
- When you uninstall from Add/Remove programs the normal UILevel is also 3 – basic user interface. This means the InstallUISequence is also skipped.
- If you double-click the MSI and run uninstall, your GUI level is 5 – full GUI. The same happens if you select “Change” in add/remove programs.
In summary, it is possible for bugs to occur in only one of the modes (silent / non-silent) because the MSI’s user interface sequence is skipped along with all its custom actions for certain user interface levels. In other words, a product could work when installed interactively and fail when installing silently (or vice versa), if the MSI is badly designed.
It is also possible to condition custom actions in the main MSI installation sequence erronously based on this UILevel feature so that results differ based on installation mode. I have seen people spawn dialogs from code in custom actions placed in the main installation sequence (where no interactivity is allowed) and then use UILevel checks to suppress the dialog in silent installation mode (or they forget that as well, triggering a hidden modal dialog that stops the install dead when running in silent mode). These weird design constructs cause unexpected installation behavior based on how the install is triggered and run.
Though this is sort of not an answer to what you asked, a final conclusion from all of this is that if your software is intended for large corporations you should not waste your design efforts on an advanced GUI for your setup as it is likely never to be used for large-scale deployment scenarios. Rather you should parameterize your installer with public properties that can be set at the command line or via a transform so that your installer can be controlled easily without running it interactively. See this post: How to make better use of MSI files.
Since I have gone so far beyond your question, I should also note that some advanced installers intended for server installations may (with moderation) benefit from a good GUI to help people quickly get your server software installed and tested. These installers tend to meddle with very advanced features such as IIS, MS SQL, AD, etc… and some interactivity could be desired for knowledgeable system administrators. But as the saying goes “most things can default” and good default settings are generally easier for people to get installed and tested whether knowledgeable or not. Many large companies run large farms of server virtuals these days (one virtual server per use case), so even server installs tend to get automated for large-scale rollout and then a good parameterized installer with public properties to set is appreciated. Smaller companies may also have server virtuals (making testing easy), but they are likely to install your setup interactively accepting whatever defaults are there – at least that is my impression.
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