Are there any connections between Haskell and LINQ?

Question

I wrote some queries in C# using LINQ. After a while, I started using Haskell a little bit, which is a functional programming language (a not so popular one), and for me it

Answer 1

for me it seems that both of them are almost the same thing. But I am unsure about this. Please, if someone has used them more than me, could they tell me if they are almost the same thing regarding principles in programming ?

Yes, the design of LINQ query comprehensions was heavily influenced by the design of Haskell. Haskell expert Erik Meijer was on the C# language design committee when we designed LINQ; his insights were very valuable. (I joined the design team at the end of this process, so unfortunately I did not get to participate in all the interesting twists and turns the design went through over the years; it started being much more traditional OO than it ended up!)

If you've recently done a serious exploration into Haskell then you're probably becoming familiar with the idea of a monad. The LINQ syntax is designed specifically to make operations on the sequence monad feel natural, but in fact the implementation is more general; what C# calls "SelectMany" is a slightly modified form of the "Bind" operation on an arbitrary monad. You can actually use query comprehension with any monad, as my colleague Wes describes here, but doing so looks pretty weird and I recommend against it in production code.

Also, could LINQ be considered functional programming ?

Yes, LINQ is heavily influenced by ideas from functional programming. It is designed to treat functions as first-class objects, to emphasize calculation over side effects, and so on.