Xamarin-android: Android app build fails when referencing package (e.g. Entity Framework Core 2.1) that depends on newer System.Memory

[cwrea]

Steps to Reproduce

1. Download, extract, and load the sample solution in Visual Studio 15.7.2.
   AndroidEFCore21Soln.zip

2. Build and run the project.

Expected Behavior

The project should build and run.

Actual Behavior

The project won't build. The build fails with the following error:

1>C:Program Files (x86)Microsoft Visual Studio2017CommunityMSBuildXamarinAndroidXamarin.Android.Common.targets(1590,2): error : Exception while loading assemblies: System.IO.FileNotFoundException: Could not load assembly 'System.Memory, Version=4.0.1.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'. Perhaps it doesn't exist in the Mono for Android profile?

EF Core v2.1 or one of its dependencies in turn depends on package System.Memory v4.5.0, while the build appears to be trying to link the app with v4.0.1.0 of the System.Memory assembly.

The previous release of EF Core, v2.0.3, could be included in a Xamarin.Android project without causing this problem. If you change the sample solution to refer to package Microsoft.EntityFrameworkCore.Sqlite v2.0.3 instead of v2.1, the project builds and the app runs as expected.

Version Information

Microsoft Visual Studio Community 2017 
Version 15.7.2
VisualStudio.15.Release/15.7.2+27703.2018
Microsoft .NET Framework
Version 4.7.02556

Installed Version: Community

Visual C++ 2017   00369-60000-00001-AA398
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ASP.NET and Web Tools 2017   15.0.40511.0
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ASP.NET Web Frameworks and Tools 2012   4.0.21208.0
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ASP.NET Web Frameworks and Tools 2017   5.2.60419.0
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Azure App Service Tools v3.0.0   15.0.40424.0
Azure App Service Tools v3.0.0

C# Tools   2.8.2-beta6-62916-08. Commit Hash: 2ad4aabc7a9dada097e54e544ebba48ab1c05074
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Mono Debugging for Visual Studio   4.10.5-pre (ab58725)
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Node.js Tools   1.4.11027.3
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NuGet Package Manager   4.6.0
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Open Command Line   2.1.179
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Visual F# Tools 10.1 for F# 4.1   15.7.0.0.  Commit Hash: 56f97a8dd4353d897336941f3e644423b87c794f.
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Visual Studio Tools for Universal Windows Apps   15.0.27703.2018
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Xamarin   4.10.0.448 (4373404db)
Visual Studio extension to enable development for Xamarin.iOS and Xamarin.Android.

Xamarin Designer   4.12.270 (82d750d12)
Visual Studio extension to enable Xamarin Designer tools in Visual Studio.

Xamarin.Android SDK   8.3.0.19 (HEAD/342b2ce96)
Xamarin.Android Reference Assemblies and MSBuild support.

Xamarin.iOS and Xamarin.Mac SDK   11.10.1.178 (408d357)
Xamarin.iOS and Xamarin.Mac Reference Assemblies and MSBuild support.

Build Logs

1>------ Build started: Project: AndroidEFCore21, Configuration: Debug Any CPU ------
1>  AndroidEFCore21 -> D:\Projects\AndroidEFCore21Soln\AndroidEFCore21\bin\Debug\AndroidEFCore21.dll
1>C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(1590,2): error : Exception while loading assemblies: System.IO.FileNotFoundException: Could not load assembly 'System.Memory, Version=4.0.1.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'. Perhaps it doesn't exist in the Mono for Android profile?
1>C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(1590,2): error : File name: 'System.Memory.dll'
1>C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(1590,2): error :    at Java.Interop.Tools.Cecil.DirectoryAssemblyResolver.Resolve(AssemblyNameReference reference, ReaderParameters parameters)
1>C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(1590,2): error :    at Xamarin.Android.Tasks.ResolveAssemblies.AddAssemblyReferences(DirectoryAssemblyResolver resolver, ICollection`1 assemblies, AssemblyDefinition assembly, Boolean topLevel)
1>C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(1590,2): error :    at Xamarin.Android.Tasks.ResolveAssemblies.Execute(DirectoryAssemblyResolver resolver)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
========== Deploy: 0 succeeded, 0 failed, 0 skipped ==========

Projects build report:
  Status    | Project [Config|platform]
 -----------|---------------------------------------------------------------------------------------------------
  Failed    | AndroidEFCore21\AndroidEFCore21.csproj [Debug|Any CPU]

Time Elapsed 00:00:07.753

Log File

adb logcat output is not applicable as the app didn't even build.

Example Project

AndroidEFCore21Soln.zip

[cwrea]

FWIW, earlier I had filed a similar issue for Xamarin.iOS: iOS app build fails when referencing package (e.g. Entity Framework Core 2.1) that depends on newer System.Memory.

[JonDouglas]

In 15.7.3 we added a facade for new System.Memory. That should fix this issue. See the following PR:

https://github.com/xamarin/xamarin-android/pull/1509

You can additionally use the Jenkins 15.7 build for a current workaround:

https://jenkins.mono-project.com/view/Xamarin.Android/job/xamarin-android-builds-d15-7/

Note: 15.7.3 just went live. Feel free to update and try it out.

[JonDouglas]

@cwrea I can confirm that your sample project compiles on 15.7.3. Please let me know if you encounter the same.

[divega]

@JonDouglas it seems that https://github.com/dotnet/corefx/issues/29847 is being considered for patch .NET Core 2.1.1 with the purpose of addressing issue with System.Memory on Xamarin.

Just to be sure, is that independent of https://github.com/xamarin/xamarin-android/pull/1509? Are these changes being coordinated?

[JonDouglas]

@divega I believe the difference is that #1509 adds the facade assemblies that will start being "ignored" once Mono removes the respective placeholders described in https://github.com/dotnet/corefx/issues/29847

I will defer to @jonpryor to correct me and answer the question on upstream coordination.

[cwrea]

@JonDouglas I just updated to 15.7.3 and re-tested the sample project. I can also confirm it is working now. Thank you!

(FWIW, the similar iOS issue I opened still needs its own fix. 15.7.3 didn't change the Xamarin.iOS behaviour.)

[JonDouglas]

I'm closing this issue based on confirmation from @cwrea. Please feel free to open a new issue if anything comes up.

[davefxy]

I downloaded and compiled the sample : AndroidEFCore21Soln.zip using (PC) vs 2017 v15.8.4, Microsoft.EntityFrameworkCoe.Sqlite v2.1.3, Xamarin.Android.Support.Design v27.0.2.1. I got the following error:
Error Can not resolve reference: System.Buffers, referenced by System.Memory. Please add a NuGet package or assembly reference for System.Buffers, or remove the reference to System.Memory. AndroidEFCore21

[JonDouglas]

@davefxy

It seems that Microsoft.Extensions.Caching.Memory > Microsoft.Extensions.Caching.Abstractions > Microsoft.Extensions.Primitives > System.Memory > System.Buffers is resolving a 4.4 version instead of 4.5 and thus you may have to manually install https://www.nuget.org/packages/System.Buffers/ 4.5 to your project.

Successfully installed 'System.Memory 4.5.1' to AndroidEFCore21
Successfully installed 'System.Buffers 4.4.0' to AndroidEFCore21
Checking compatibility for System.Buffers 4.4.0 with MonoAndroid,Version=v8.1.

I believe this is a separate issue from this this thread. Can you file a new issue in our repo?

Thanks!

[davefxy]

You are correct. Your solution worked. I had previously tried this but was not able to locate system.buffers because I probably misspelled it.
Thank you very much