System.MissingMethodException when using certain methods from FSharp PowerPack and compiling to a Class Library

Question

So I'm just getting started with F#, and I'm encountering a very weird issue where I get a System.MissingMethodException thrown when using certain methods from the FSharp PowerPack.

This does not happen for all methods in the same module. It also does not happen if I compile my assembly as an Application instead of a class library.

Reproduction steps:

1. Create 2 assemblies, one Class Library and one Application.
2. Add nunit.framework and the FSharp.PowerPack DLLs as references to both assemblies.

3. Create the following test fixture in each assembly.

   open NUnit.Framework
   
   [<TestFixture>]
   type Tests() = class
   
       [<Test>]
       member self.OfSeq() =
           // Will always succeed
           Matrix.Generic.ofSeq [[1]] |> ignore
   
       [<Test>]
       member self.OfList() =
           // Will fail under certain conditions with a System.MissingMethodException
           Matrix.Generic.ofList [[1]] |> ignore
   end
   

4. Compile both assemblies.
5. Open each assembly in NUnit and run all the tests.

When I do this the Application runs just fine (all tests pass), but the Class Library fails with the following exception:

System.MissingMethodException : Method not found: 'Microsoft.FSharp.Math.Matrix`1<!!0> Generic.ofList(Microsoft.FSharp.Collections.FSharpList`1<Microsoft.FSharp.Collections.FSharpList`1<!!0>>)'.
   at Temp2.Tests.OfList()

What is going on here?

Another method that produces the issue is matrix.PermuteColumns.

Additional Info:

• I'm compiling both assemblies for .NET 4.5
• I'm compiling using Visual Studio 2012 RC
• I'm using NUnit version 2.5.10.11092
• I'm using FSharp PowerPack version 2.1.3.1 (though the DLL properties state that it's 2.0.0)

Let me know if there's additional information that would be of use.

Stairhead

I believe the F# Powerpack DLLs are only compiled for .NET 2.0; if you want them to run 'natively' under .NET 4.0 or 4.5, you'll have to download the sources and build the assemblies yourself. – Crib

Answer 1

I wonder if this is related to binding redirects. You may need to copy the app.config in the application project to the library project.

This sounds similar to a known issue that I'm currently writing a blog post about for the F# team blog (probably to appear in the next few weeks) regarding MSTest rather than NUnit. I would try copying the app.config into the library project, and if that doesn't work, then use the online template for unit testing here:

http://visualstudiogallery.msdn.microsoft.com/51ebe64a-899b-4959-8c24-b0148ed6b264

and additionally select 'TEST\Test Settings\Select Test Settings File' from the menu in VS, and point it at the 'MSTest.runsettings' file included in the unit test project template. I expect that one of those two tweaks will fix it in the MSTest case.

Eggett

Copying the app.config fixed the issue. I'll keep an eye out for the blog post. Thanks for the help. – Stairhead

same here, even though i did a machine wide redirect. there must be something else. those pesky issues are quite annoying. – Necessitarianism

Different solution found when using VS2013 Preview and latest (V1.3) "F# MsTest Project": see my answer. – Efficiency

Answer 2

(Answer for future reference since this Q was the first hit on searching.)

With Visual Studio 2013, with the "F# MSTest" online project template referenced by Brian, neither of Brian's suggestions helped (for a start the target of the testing is a library project without App.Config).

However I eventually found that the test project was set to use F#3 runtime (with FSharp.Core V4.3.0.0). Changing this to F# v3.1 (FSharp.Core V4.3.1.0) fixed the issue.

Efficiency

This answer helped me - thanks for adding it to the question. – Spirituality