Add a new C# operator "in" to check if an item is in the data structure.

[mckabue]

dotnet/roslyn#37037 (comment)

[Tom01098]

So, where would this be used? Is it essentially an alias for a Contains method on the type? Is there an underlying interface for this behaviour?

[yaakov-h]

Duplicate of #1665.

[mckabue]

@Tom01098
Yes, operator in would be an alias to Contains.

We could however also use it with reflection to check if a property with a given name exists in an object, or class. Just like in operator in JavaScript

[orthoxerox]

@mckabue reflection is something that should not be this convenient to use. It bypasses a lot of the safeguards built into C# and is much slower than regular programming. Its syntax is all "I understand the risks and want to proceed" by design.

[Tom01098]

@mckabue This would definitely never be implemented with reflection as it bypasses type safety.

If it's just an alias for Contains, then why not just use that? You're just saving a few characters and flipping the order; I know 'I don't like it' is a weak argument, but I think this ordering is less clear, especially as in doesn't really imply this behaviour.

[mckabue]

@Tom01098 I have nothing against Contains, I would just like an alternative.
Also, I had a friend who was moving from python to C# and was asking why there is no in operator, generally to make it easy to transition from a language with similar syntax.

[john-h-k]

But why?

if (1 in someArr)

if (someArr.Contains(1))

It doesn't add much, it is just some syntactic sugar which is kinda ... useless. Why make an alternative for no reason? A proposal needs to be valuable to be accepted into the lang

[Tom01098]

Also, I had a friend who was moving from python to C# and was asking why there is no in operator, generally to make it easy to transition from a language with similar syntax.

They're moving from a quite different language, C# isn't python v2 :)

Adding new ways of doing the same thing means people will have to learn both when reading and maintaining code, making it harder to do both.