Merge two mst transform files

Question

Hi,
I have two mst files and I need to merge both and create a single transform file and then apply it over an msi. How can I achieve this using C#?
Any code snippet would help.
Regards,
Pradeep R

Answer 1

If you have an original database (.msi) to which the transforms apply, then I think you can do this:
Copy the original database to a new file. (Or perhaps you can use the szPersist parameter of MsiOpenDatabase to skip this step.)
P/Invoke MsiOpenDatabase to open the copy database.
P/Invoke MsiDatabaseApplyTransform to apply each transform (.mst) to the copy database.
P/Invoke MsiDatabaseCommit to save the changes to the copy database.
P/Invoke MsiOpenDatabase to open the original database.
P/Invoke MsiDatabaseGenerateTransform to compare the original database to the copy database and save the differences as a transform.
P/Invoke MsiCloseHandle twice to close both databases.
If you don't want to use P/Invoke directly, then check if Deployment Tools Foundation wraps these functions.  Alternatively, you could run the msitran.exe program in the Windows SDK.
If you don't have a suitable original database, then I guess you'll have to use the MSITRANSFORM_ERROR_VIEWTRANSFORM flag of MsiDatabaseApplyTransform and read the _TransformView table afterwards. That should give you enough information to construct a suitable
database.
Yet another approach would be to check if the WINE project has reverse-engineered the .mst file format.  If so, you could probably merge the transforms without needing an original database. IIRC they have code for reading .msi files at least. Don't
expect Microsoft to support that though.