ProjectTo NullReferenceException

[kvpt]

Hi,

I tried to upgrade AutoMapper from version 10 to 11 and after that my tests failed with NullReferenceException from AutoMapper.

I identified that the issue is caused by the global mapping that I use to convert Null string to Empty string. This method did work up to version 10.
Standard mapping is not impacted but some ProjectTo now fail.

Source/destination types

See LinqPad reproduction in attachment.

Mapping configuration

See LinqPad reproduction in attachment.

Version: 11.0.1

AutoMapper version: either 11.0.0 or 11.0.1 (10.x version are not impacted)
EFcore version : either 5.x or 6.x (not Efcore dependant)

Expected behavior

The ProjectTo method work without issue.

Actual behavior

The ProjectTo method throw an NullReferenceException.

Steps to reproduce

LinqPad reproduction in attachment, drop it to LinqPad to execute.

ProjectToIssue.txt

[lbargaoanu]

Workaround: cfg.ValueTransformers.Add<string>(val => val ?? "");. That's instead your string converter.

[kvpt]

I confirm this approach fix the issue.
And I also think that it's a better way to assign empty value to a string than having to create a profile just to do this one thing, so I don't see that as a workaround but as an improvement.
And thanks for the quick reply.

[lbargaoanu]

Yes, having the transformer seems better.
While I fixed the NRE, the query we generate is worse because that map exists. Maybe that could be fixed too, but I'd rather not try that at this time :)

[github-actions]

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