Abel Braaksma

Re-reading this thread and @dsyme mentioning tuples in this https://github.com/fsharp/fslang-suggestions/issues/213#issuecomment-471196625, and considering and testing the last comment by @Tarmil, [this seems to be correct](https://sharplab.io/#v2:DYLgZgzgNAJiDUAfA9gBwKYDsAEBlAnhAC7oC2AsAFCnIwCuw62AKgE74CyTAvFdv9kZFsACkQBBRACFEAYUQARRAFFEASmwAPbL0oD92AJZgtO7ABYATNiIALLNnF8D/dMGOnuFgMw37OKWcXNw9tL3NzPwdZIIMQkzCLAFYonAVY/TcIJmUMgVihbDARDV0XflIAQyIAY1tsAE4G7AB3Qzs8/kRHbABaAD5sACIAc2RaIc7sbqk+waGAI0qYSb1y7tk54dlV8unsBS2hhV317GUj5SGgA=). As in, there's no (direct) relation...

Something seems to have gone wrong with the layout of the code sections of your post, can you edit for readability? And you mention "some exception", can you paste the...

Btw, why do you want to use [DefaultAugmentationAttribute](https://github.com/MicrosoftDocs/visualfsharpdocs/blob/master/docs/conceptual/core.defaultaugmentationattribute-class-%5Bfsharp%5D.md) with `false`? It removes the code normally generated for proper operation of the DU, and I think you'd then have to write...

> Well, I'd made a custom Option shared in C# and F#, so that the C# project won't import the FSharp.Core.dll, and when I update the 'FSharp.Core.dll' in F#, the...

> Option type is an exception, it's simple and important. Because F# is inconvenient to handle refrence type null and Nullable(). Instead of exposing option, may I suggest to expose...

> But how to give a option value to C#? If use Option.toObj, I should use AllowNullLiteral I don't. You shouldn't expose `Option`. If you need to return a value...

> But when C#8.0 released. It was released in September 2019, along with Visual Studio 2019, 16.3. That it isn't enabled by default allows you to migrate one by one....

@greatim, perhaps I was describing it all a little too abstract. Interfaces in F# are guarded for `null`, but in C# they aren't, so when you have a function that...

Indeed, and clearly separate what you're exposing to C#, and what you're internally using. That way you keep all the freedom and don't have to worry about what you can...

@ninofloris? You mean when using `DefaultAugmentation`? I don't know if it's possible to create a useful DU if you have to create all helpers by hand. Why not just use...