Correct version of Fsharp.Core

Solution 1:

You should not be obtaining FSharp.Core from nuget. Microsoft does not publish any official F# bits to nuget today (though this could potentially change in the future). It's common for 3rd-party packages to bundle FSharp.Core (since presumably that's the version used for testing/validation of that 3rd-party component), but nuget should not currently be used as a mechanism for getting FSharp.Core updates or new versions.

The versioning story for FSharp.Core is sadly rather complex, and definitely not as simple as "higher version means newer." A key thing to realize is that there are 2 axes - what F# version does the runtime support, and what .NET framework version/profile does it target.

Below are the official FSharp.Core versions that ship with VS 2013 (find these dropped under %ProgramFiles(x86)%\Reference Assemblies\Microsoft\FSharp).

• 4.3.1.0 (F# 3.1/.NET 4) This is the most recent official version. Unless you have a requirement to target .NET 2, or you are using some legacy F# component that won't work with 3.1, this is the version you should use for any new desktop app.
• 4.3.0.0 (F# 3.0/.NET 4) These are the same bits that shipped with VS 2012. It is included so that you can continue working on F# 3.0 projects in VS 2013 without retargeting them to 3.1. You should use this if you have a legacy F# 3.0 desktop project that you are not ready to move to 3.1 yet.
• 2.3.0.0 (F# 3.0/.NET 2) These are the same bits that shipped with VS 2012. The only reason to use this is if you are targeting .NET 2. The .NET 2 side of things is not being developed further, btw - new features, versions, etc will be done for FSharp.Core targeting .NET 4+; the .NET 2 FSharp.Core is still fully supported, but it is frozen.
• 3.3.1.0 (F# 3.1/"Portable") This version targets .NET portable profile 7 (.NET 4.5/Windows Store). Use this if you are creating a component for a Windows store app and you don't care about Silverlight. This profile is newly supported in VS 2013.
• 2.3.5.1 (F# 3.1/"Portable (Legacy)") This version targets .NET portable profile 47 (.NET 4/Silverlight 5/Windows Store). Use this if you are creating a Silverlight component. This profile was also supported in VS 2012, and referred to at that time as simply "Portable."
• 2.3.5.0 (F# 3.0/"Portable (Legacy)") This version targets .NET portable profile 47 (.NET 4/Silverlight 5/Windows Store). These are the same bits that were included in VS 2012. Included in VS 2013 to enable you to continue working on F# 3.0 portable/silverlight projects.

.NET portable profiles are a big PITA and cause a ton of complexity. This site has a good summary to help understand: http://blog.stephencleary.com/2012/05/framework-profiles-in-net.html

So for your specific scenario (new console app) use 4.3.1.0.

Edit 7/2015:

Here's a table that probably explains the story better than the wall of text above. I've tried to use colors to indicate the motivation for the version numbers. You'll see the versioning of the portable libraries was a bit ad hoc and inconsistent in VS 2012 and 2013, but is finally consistent and predictable starting with VS 2015. This is up to date with F# 4.0, which just released.

Solution 2:

Today I would probably rather follow these guidelines

In short, you can/should reference FSharp.Core from NuGet