Using `dynamic` keyword in C# doesn't compile

Question

I'm trying to compile a piece of C# code that contains the dynamic keyword. (I need this keyword for using ironpython.) However, it doesn't compile, complaining that

error CS1980: Dynamic keyword requires 
`System.Runtime.CompilerServices.DynamicAttribute' to be defined.
Are you missing System.Core.dll assembly reference?

The compiler I'm using is Mono JIT compiler version 2.10.8.1. I don't have System.Runtime.CompilerServices.DynamicAttribute in the list of possible references.

How can I make mono accept the dynamic keyword?

Leucine

Do you have Mono's System.Core.dll referenced? – Alchemize

Did you add references to System.Core.dll, Microsoft.Dynamic.dll and Microsoft.CSharp.dll? – Dung

@Dung don't have either of them in my list. – Leucine

You need to enable the C# 4 profile, sounds like you didn't. Google "__enable_profile4=yes" – Osteogenesis

Thanks, I started working on an existing project that appeared configured to work with C# 2.0. -_- – Leucine

You shouldn't NEED the dynamic keyword in your C# code. – Easterly

@Easterly Please read the question before commenting. It's about working together with IronPython. The dynamic keyword is simply needed for that. – Leucine

I was chasing the misinformation that you needed dynamic keyword in using the IronPython engine. You can instantiate the engine and expose typed objects to it. I haven't used the dynamic keyword in its context yet. You may need it to get objects back from the python. But it doesn't HAVE to be used that way. – Easterly

The latter is exactly my use case. I need to retrieve python objects from a python library into the C# part. – Leucine

So that use case you do need the keyword and .NET 4.0+. No bad blood was intended bro. Is this case closed? You should followup with a minipost and close it yourself. I just learned a lot about embedded IronPython and was browsing the not closed list. – Easterly

Yeah, IronPython is an interesting technology. By the way, you are right that I should've marked this question as answered. Will do. – Leucine

Answer 1

This comment of Hans Passant solved the problem:

You need to enable the C# 4 profile, sounds like you didn't. Google "__enable_profile4=yes"

Leucine