[wix-users] Merge changes for Config files and IIS settings

Ven H venh.123 at gmail.com
Mon Mar 4 02:28:55 PST 2019

Does anyone have any inputs? Please help.

On Fri, Feb 22, 2019 at 11:26 AM Ven H <venh.123 at gmail.com> wrote:

> I have a business requirement. I know many eyebrows will be raised, but
> unfortunately, I need to achieve this requirement.
> There is an application folder that already exists (which was probably
> installed by some other MSI). Now, I have to install the same application
> folder using my MSI. The application folder has a lot of config files.
> Since the end customer would have made some changes to this config, my MSI
> should not overwrite these files. But, the config file changes from my MSI
> should be merged from my MSI. For this, I think I may have to use a Custom
> Action. However, I have the following challenges / questions.
> 1. If a file already exists and my MSI also has the same file to be
> installed, will the file from MSI overwrite the existing file? If so, can
> this be prevented selectively ( I don't want some selected files like
> config files to be overwritten) by using NeverOverwrite attribute (Will
> NeverOverwrite work on files outside of MSI, i.e., the files already
> present and not installed by MSI or it will work 2nd time when the same MSI
> is being installed or upgraded)?
> 2. Let's say this file is not overwritten and merged using Custom Action,
> what will happen when I run an Upgrade again using my MSI? Will it
> overwrite the other files (config file components will have NeverOverwrite
> attribute and hence they will be spared, I believe)?
> 3. I have similar requirement for IIS (web sites and app pools). They
> might have been created manually or using another MSI. First time, when I
> run my MSI, they should not be recreated since the end customer could have
> updated some settings manually. So, I should be able to merge the changes.
> Please help / advise.

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