IIncrementalGenerator Database Examples?

[jw56578]

Is it possible to use SqlClient to query sql server using IIncrementalGenerator.
I have coded a prototype, but when I introduce SqlClient code into RegisterSourceOutput, it either throws an exception
Could not load file or assembly System.Data.SqlClient.
or the method is not called when debugging and the source code is never generated.
if I remove all reference to SqlClient code. It runs fine.

[jasonmalinowski]

Source generators should be quite fast and not have external dependencies; you should not be doing calls to external servers like SQL.

[sharwell]

External I/O (including but not limited to reading or writing files on disk) is not allowed in a source generator. All non-source inputs to a source generator need to be gathered during earlier steps of the build, and provided to the source generator through the <AdditionalFiles> mechanism in the compiler. A pre-build step to gather this information in a file could be designed to read data from an SQL server.