SignalR callbacks working on net7.0, not on net9.0

[ispysoftware]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Updating from net7.0 to net9.0 breaks all callbacks from signalr.

When running this code under net7.0 it works fine, i see "SignalR connection established." followed by messages coming in on "ProcessJSON". I change to net9.0 and I just see "SignalR connection established." - nothing is logged and no messages arrive.

Expected Behavior

Should function exactly the same as net7.0

Steps To Reproduce

See repro project

https://github.com/ispysoftware/sigrtest9/tree/main

The test fails. Change the net runtime from net9.0 to net7,0 in the project file and the test passes
Set Trimming to false and the test passes.

Exceptions (if any)

No response

.NET Version

net9.0

Anything else?

No response

[ispysoftware]

It's due to trimming - working in net7.0 with trimming enabled. Broken in net8.0 with trimming enabled
<PublishTrimmed>true</PublishTrimmed>

#41704

Is there any workaround using TrimmerRootAssembly?

[BrennanConroy]

Trimming isn't supported for SignalR in .NET 8.

[ispysoftware]

@BrennanConroy - yes i've spent 3 days finding that out. Do you know if it's supported in .NET 9? The reason I ask is that with trimming our client facing app is 50mb and without it it's 140mb.

publishing a trimmed app with signalr on net8.0 doesn't give any trim warnings.

[BrennanConroy]

#41704 (comment)

[ispysoftware]

Thanks @BrennanConroy .
Spent the last 3 days updating our codebase to be compatible with net9.0 and having exactly the same issue with SignalR.
Just says
"SignalR connection established" and nothing else. No messages back from it.

I've linked a repro demonstrating the issue to
#41704 (comment)

[BrennanConroy]

You are still using the 8.0 package... Trimming support was added in the 9.0 version which means you need the 9.0 package.

[ispysoftware]

Thanks @BrennanConroy - I updated the reference to the latest pre-release. Same issue.