Backwards Compatibility Broken with IOptionsSnapshot when upgrading to .Net Core 2.0 about options

[HaoK]

We changed the implementation/behavior of IOptionsSnapshot entirely in 2.0, we basically repurposed the type name as its still meant to be used to capture the state of an options instance for the lifetime of a request, instead of having a lifetime timed to the IOptionsMonitor

I can help you migrate to 2.0 if you get stuck, IOptionsMonitor is still mostly the same in 2.0. Were you using snapshot for getting updating/reloading options?

[Aurel]

Hey @HaoK - I'm quite well aware that the IOptionsSnapshot has changed, but in the process of changing, did the backwards compatibility break? Essentially, my old class libraries that I have just don't work with NetCore 2.0 apps. Let's say that I need my class libraries to remain as < 2.0 NetStandard apps.

Yes, originally, I was using snapshot for reloading options on the fly. Is that not what it does anymore? In the case, the documentation is a bit out of date and should reference that. Does this also mean that my old class library that has all of this functionality can only work with older versions of .net core, and not with newer ones?

I've come up with a number of fixes, and I got it working, but the fixes are hacky, and force me to use dynamic everywhere so I can try calling .Value, and if that throws I can try calling .Get(string.Empty), even though I'm in a NetStandard1.3 app that doesn't have that function. It's one way I've found of solving this problem. However, I'm just trying to report that something goes horribly wrong here.

Additionally, it only happens if the options are requested by a Service. If I just request the options themselves, not much is happening, but if I request a service, and in its constructor requests the POCO object I showed above, I consistently get this error about MissingMethodException

[HaoK]

@Aurel yes, the 2.0 IOptionsSnapshot type is not backwards compatible with 1.0 at all

[Aurel]

Interesting - I've found a fix locally that uses a bunch of dynamics so I don't have to know about the type I'm invoking, but can you explain to me then, why this might be happening? I don't understand why the get_Value() method would be missing, when it's clearly there both in 1.1.2 and in 2.0.0! (In 2.0.0 it's inherited from IOption<T>)

[aspnet-hello]

This issue was moved to dotnet/aspnetcore#2387