[mquander]

Strictly speaking, none of those features were necessary to implement LINQ. Anonymous functions were already possible in C# 2.0 with the ugly delegate syntax. Type inference saves a lot of keystrokes, and anonymous types save big families of generic tuple types, but you could do without -- hell, people write functional Java.

(A better comparison would be to look at LINQ-to-SQL specifically; that would not be possible in any sense without the expression tree libraries and compiler support introduced in C# 3.0, since there was no way to "quote" a C# expression and look into it. That's much closer to the mark here.)

However, I agree with you in spirit. A big enough quantitative difference becomes a qualitative one; nobody would actually want to use LINQ+C#2. And likewise, few people want to write small-scale DSLs in C#.

[DougBTX]

Well, your argument is tiptoeing down a very narrow path based on the definition of "necessary". Here's what Eric Lippert has to say about which features were necessary for LINQ: http://blogs.msdn.com/b/ericlippert/archive/2009/10/05/why-n...

[prospero]

Yes, you're right. Expression trees are especially interesting from an integrated DSL perspective, since you can do ridiculous things like turn lambda expressions into a syntax for hashes and so on. I omitted them because I believe that really did require a runtime modification to support.

But I would argue that since DSLs are all about affordances, it's not sufficient to say that similar functionality would be "possible". If the new approach doesn't represent significant semantic compression (which your hypothetical LINQ+C#2 would not), no one will use it. By that measure, the syntactic sugar added to C# 3.0 was absolutely a necessary precondition for LINQ.