How to include MEF in Unity 2020 LTS ? (resolved)

Question

I tried to include MEF library in Unity 2020 LTS

My project settings

Scripting Backend: Mono

Api Compatibility Level: .Net Standard 2.0

Here are my steps to try and include an external library:

nupkg has been loaded from nuget.org
Then i got the system.componentmodel.composition.5.0.0.nupkg
And when i unpacked .nupkg file i got netstandard2.0/System.ComponentModel.Composition.dll
Then i added System.ComponentModel.Composition.dll to Assets folder
Then i got this error messages in console:

Error: Could not load signature of System.ComponentModel.Composition.Hosting.CompositionContainer:ReleaseExports due to: Could not resolve type with token 0100003c (from typeref, class/assembly System.Lazy`2, netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51) assembly:netstandard, Version=2.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51 type:System.Lazy`2 member:(null) signature:

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Some people say to create mcs.rsp file, which is now called scs.rsp as far as I understand.

And inside the file you have to add this line, it is only valid for mcs.rsp :

-r:System.ComponentModel.Composition

And for the file scs.rsp it should be correct:

-r:System.ComponentModel.Composition.dll

But I found Unity3d Manual page Referencing additional class library assemblies

And the following was written inside:

If your Project uses the .NET Standard

API Compatibility Level, you don’t need to take any additional steps to

use part of the .NET class library API.

Does this mean that I do not need to perform any additional steps in order for the library to start working?

It would be great if someone could help with this issue.

I have already tried the following points, but nothing works:

different versions of Unity (2018 LTS, 2019 LTS)
different versions of Api Compatibility Level (.Net 4.0)
creating scs.rsp file
creating mcs.rsp file

Answer 1

Best Answer

Answer by Akeyn · Apr 06, 2021 at 11:29 AM

I was able to make the library work.

I was looking for a solution for a long time, came across the fact that this library is contained in .NET 4.x and I had to figure out how to import library it better, and I found a very simple solution it is take the library from the Unity folder and drop it into the Assets folder

Steps to import .dll

I took the System.ComponentModel.Composition.dll library along the following path C:\Program Files\Unity\Hub\Editor\2020.3.2f1\Editor\Data\MonoBleedingEdge\lib\mono\unityjit
Then I changed the Api Compatibility Level from .NET Standard 2.0 to .NET 4.x
Voila everything works.

If it was helpful, please like it ;)

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krupps · Nov 08, 2021 at 05:46 PM 1

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OMG, you are such a life saver! Why .Net Standard doesn't work, but I did notice even though the api is pointed to 2.0, the Unity project is still 4.7.1. I did did my library in 4.7.1, which was a pain since VS 2019 doesn't allow you too. I did all your recommendations and Finally I have my DryIoc using DI on all my game objects. Kudos!

How to include MEF in Unity 2020 LTS ? (resolved)

My project settings

Here are my steps to try and include an external library:

Search for information

It would be great if someone could help with this issue.

1 Reply

I was able to make the library work.

Steps to import .dll

If it was helpful, please like it ;)

Your answer

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