F＃在.fs VS .fsx文件中编译VS Intellisense

Question

Visual Studio 2015, same F# 4.0 Console application. Two files, a Program.fs file and a Script.fsx script file with the same code:

open FSharp.Core
open Microsoft.FSharp.Collections

let seq = seq { 1 .. 3 }
let seqItem1 = Seq.nth(0) seq
let seqItem2 = Seq.item(0) seq

• Program.fs will not compile: ".item" constructor method not defined. No further messages from intellisense.
• Script.fsx works fine but Intellisense prompts that Seq.nth is deprecated, use Seq.item instead.

Answer 1

In my case, this was due to the fact that I created the Project originally on VS 2015, but then for a while I had to work on VS2017. When switching to 2017, FSharp.Core could not be found between the project references for some reason -- I then added another reference to it, however I (wrongly) kept the old reference to the dll.

Switching back to VS2015 brought back the old FSharp.Core reference together with the other one added in VS2107. This resulted in the behavior stated in the question.

I still have to test whether bringing back the project to VS2017 will result in the FSharp.Core reference to not found again and the reason behind that.