[DevCom] No way to resolve conflict with mscorlib

[grendello]

Developer Community issue: https://developercommunity.visualstudio.com/content/problem/356750/no-way-to-resolve-conflict-with-mscorlib.html

Original post:

Installed VS 15.8.7 and tried to compile my existing Xamarin Forms app after updating it to 3.3.0-pre3, but I'm having issues with Android compilation. Looks like there is some kind of version conflict with mscorlib.

1>------ Rebuild All started: Project: TestClient, Configuration: Debug Any CPU ------
1> Fody: Fody (version 3.2.9.0) Executing
1> Fody: Searched for 'PropertyChanged'. Found: C:\Users\xyz.nuget\packages\propertychanged.fody\2.5.13\build..\netclassicweaver\PropertyChanged.Fody.dll
1> Fody: Finished Fody 172ms.
1>TestClient -> C:\s\Test\TestClient\TestClient\TestClient\bin\Debug\netstandard2.0\TestClient.dll
1> Fody: Skipped Verifying assembly since it is disabled in configuration
2>------ Rebuild All started: Project: TestClient.Android, Configuration: Debug Any CPU ------
2>C:\s\Test\TestClient\TestClient\TestClient.Android\FodyWeavers.xml : warning XA0101: @(Content) build action is not supported
2> Fody: Fody (version 3.2.9.0) Executing
2> Fody: Searched for 'PropertyChanged'. Found: C:\Users\xyz.nuget\packages\propertychanged.fody\2.5.13\build..\netclassicweaver\PropertyChanged.Fody.dll
2> Fody: Finished Fody 173ms.
2> TestClient.Android -> C:\s\Test\TestClient\TestClient\TestClient.Android\bin\Debug\TestClient.Android.dll
2> Fody: Skipped Verifying assembly since it is disabled in configuration
2> No way to resolve conflict between "mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" and "mscorlib, Version=2.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e". Choosing "mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" arbitrarily.
2>COMPILETODALVIK : PARSE error :
2>COMPILETODALVIK : PARSE error :
2>COMPILETODALVIK : PARSE error :
2>COMPILETODALVIK : PARSE error :
2>COMPILETODALVIK : PARSE error : 

[jonathanpeppers]

So the real error here was:

COMPILETODALVIK : PARSE error :

The ExoPlayer library has Java 8 bytecode.

Closing, since they also appear to solve the problem here by using d8 in Visual Studio 2019 Preview 2.