hostfxr_run_app & hostfxr_get_runtime_delegate

[wingchunninja]

Hi everyone,

I have a .net6.0 application that I call from unmanaged code.
What works is using hostfxr_get_runtime_delegate and then calling functions from a particular component.

If I call only hostfxr_get_runtime_delegate, I have the problem that the Main/Startup classes from my .net application are not being called, and that leads to the point where crucial things that I use in the component class are not being initialized.

Is there a possibility to first call hostfxr_run_app and then hostfxr_get_runtime_delegate. What I have tested is that calling hostfxr_run_app works and initialized the app, but after that calling hostfxr_get_runtime_delegate on the same contextHandle results into me receiving an EXC_BAD_ACCESS (code=1, address=0x986d41350c08).

Do you have some ideas how i can use a hybrid from both, initializing the app and after that calling the component?

[vitek-karas]

The hostfxr_run_app will only return once Main returns at which point the runtime shuts down. So using stuff after that is not possible.

There are two possible solutions if you need to have:

• Custom host - so that you control how the runtime is loaded
• Running managed app inside the process

1. You could just call Main as a normal method. This comes with some gotchas:

• Normally Main will not return until the app is done, so may want to do this on a new thread and let it sit there (depends on what it does)
• Some things will not be initialized the same way they would be with hostfxr_run_app. For example things like Environment.GetCommandLineArgs will not return any value. It's unlikely this would be a problem, but it can.

2. A cleaner solution is to use hostfxr_run_app and then:

• The managed code calls back into native - typically via PInvokes
• It passes a native function pointer to some managed method which the native code stores
• Native code then can call into managed using the native function pointer at any point
  (This is roughly what ASP.NET does when being hosted inside IIS)

[wingchunninja]

Thanks, i already did approach 1. But I think i will try the second one as well.