Issue with RC1 package

[Lentolo]

Hi everyone 👋
At our company, we’re building an ASP.NET Core API backed by a PostgreSQL database, using Fluent NHibernate for data access.
We’re currently migrating to .NET 10, which means all our NuGet packages are being updated as well. We’ve run into an issue with the RC-1 release of the Npgsql driver.
To reproduce the problem, we’ve put together a minimal console app with a single table defined like this:

• id: int, auto-increment
• code: string (50 chars), not null
• description: string (200 chars), nullable
• validfrom: DateOnly, not null
• validto: DateOnly, nullable
• enabled: bool, not null
• price: double, not null

The app simply inserts a record, reads it back, and deletes it.
Everything works fine with this package set:

<PackageReference Include="NHibernate" Version="5.6.0" />
<PackageReference Include="FluentNHibernate" Version="3.4.1" />
<PackageReference Include="Npgsql" Version="9.0.4" />

But when switching to the 10.0.0-tc.1 we get the following error:

System.FormatException: Input string '24/10/2025' was not in the correct format.
...
Inner Exception:
InvalidCastException: Unable to cast object of type 'System.DateOnly' to type 'System.IConvertible'.

We’re aware this is a pre-release package, but we wanted to flag the issue in case it helps others or maintainers.
Thanks!

NHibernatePostgresApp.zip

[vonzshik]

That's because starting with npgsql 10 we return DateOnly by default (#5328). You have two options: either wait for nhibernate/nhibernate-core#2912 or write your own methods to read/write DateOnly instead of relying on NHibernateUtil.Date.

[roji]

To add to the above, Npgsql still does support reading PostgreSQL date as DateTime - it's only that the default has changed. I'm completely unfamiliar with NHibernate, but maybe it's possible to configure it somehow to call DbDataReader.GetDateTime() (or GetFieldValue<DateTime>()) instead of DbDataReader.GetValue(). But otherwise, long-term DateOnly is the better representation for the PostgreSQL date type.

[roji]

I see that we're still missing various breaking change notes for 10 (and haven't yet published the page), I'll take care of that; otherwise I'll close this issue as expected, but feel free to post back here with additional questions etc.

[Lentolo]

Hi,
thank you for the explanation.
We created an NHibernate Custom IUserType to manage this change.
Now everything works as expected.

Ciao.