Starting with C# 7.0, there is basic pattern matching support. I want to look at using this to interop with F# Discriminated Unions, and see what consuming F# code from C# could look like at it's best.
Here is an example of an F# Discriminated Union (hereafter DU)
For those unfamiliar with DUs, the
Abc type defined above can be either
C (and nothing else), and in the case of
A there is no "payload", with
C there is a payload that comes with it.
So given that this compiles down to a sealed class, and that the cases become classes, we can use the new type pattern in C# to match this with:
There are some things to notice here:
1. It's really nice
The code here is clean I'd say, we are matching on type and can either ignore the result of the cast using
_ or we can take it as a named variable (like with
c in this example).
2. We don't get the safety we have in F#
In F#, when handling DUs the compiler ensure that we have handled all cases, in C#, these safety checks aren't enforced.
3. What about case
Yeah, so this is where it's not perfect. The F# compiler does generate a type for case
A however it is marked as internal and therefore is not accessible for us to match against, however there are a few options, I'll let you pick which is your favourite:
Let me know in the comments what your preference is, or is there a better option?
Thanks for reading!