Adding a nuget reference invalidates the project from building

[JCBurnside]

Steps to Reproduce

1. Use an existing Xamarin android app or create a new one
2. Add nuget reference to System.Runtime.Loader verison 4.3
3. Check error log

Reference example project.
https://github.com/JCBurnside/XamarianNugetReferenceErrorExample

Expected Behavior

Able to compile and run.

Actual Behavior

Throws System.BadeImageFormatException at compile time.

Version Information

Microsoft Visual Studio Community 2019
Version 16.0.1
VisualStudio.16.Release/16.0.1+28803.156
Microsoft .NET Framework
Version 4.7.03056

Installed Version: Community


ADL Tools Service Provider   1.0
This package contains services used by Data Lake tools

Application Insights Tools for Visual Studio Package   9.0.20307.1
Application Insights Tools for Visual Studio


C# Tools   3.0.0-beta4-19170-01+1deafee3682da88bf07d1c18521a99f47446cee8
C# components used in the IDE. Depending on your project type and settings, a different version of the compiler may be used.

Extensibility Message Bus   1.1.77 (master@24013d5)
Provides common messaging-based MEF services for loosely coupled Visual Studio extension components communication and integration.

Fabric.DiagnosticEvents   1.0
Fabric Diagnostic Events


Microsoft Continuous Delivery Tools for Visual Studio   0.4
Simplifying the configuration of Azure DevOps pipelines from within the Visual Studio IDE.

Microsoft JVM Debugger   1.0
Provides support for connecting the Visual Studio debugger to JDWP compatible Java Virtual Machines

Microsoft Library Manager   1.0
Install client-side libraries easily to any web project

Microsoft MI-Based Debugger   1.0
Provides support for connecting Visual Studio to MI compatible debuggers
[2019-04-19_22-11-59.18224.Ide.log](https://github.com/xamarin/xamarin-android/files/3103818/2019-04-19_22-11-59.18224.Ide.log)
Mono Debugging for Visual Studio   16.0.300 (573eda3)
Support for debugging Mono processes with Visual Studio.

NuGet Package Manager   5.0.0
NuGet Package Manager in Visual Studio. For more information about NuGet, visit http://docs.nuget.org/.

ProjectServicesPackage Extension   1.0
ProjectServicesPackage Visual Studio Extension Detailed Info

ResourcePackage Extension   1.0
ResourcePackage Visual Studio Extension Detailed Info

ResourcePackage Extension   1.0
ResourcePackage Visual Studio Extension Detailed Info

SQL Server Data Tools   16.0.61903.25110
Microsoft SQL Server Data Tools

ToolWindowHostedEditor   1.0
Hosting json editor into a tool window

TypeScript Tools   16.0.10306.2001
TypeScript Tools for Microsoft Visual Studio

Visual Basic Tools   3.0.0-beta4-19170-01+1deafee3682da88bf07d1c18521a99f47446cee8
Visual Basic components used in the IDE. Depending on your project type and settings, a different version of the compiler may be used.

Visual C++ for Linux Development   1.0.9.28711
Visual C++ for Linux Development

Visual F# Tools 10.4 for F# 4.6   16.0.0.0.  Commit Hash: 809f41207b74a1356208f11b8fa3a15233734050.
Microsoft Visual F# Tools 10.4 for F# 4.6

Visual Studio Code Debug Adapter Host Package   1.0
Interop layer for hosting Visual Studio Code debug adapters in Visual Studio

VisualStudio.Mac   1.0
Mac Extension for Visual Studio

Xamarin   16.0.0.515 (d16-0@a3502d929)
Visual Studio extension to enable development for Xamarin.iOS and Xamarin.Android.

Xamarin Designer   4.17.4.418 (remotes/origin/d16-0@3d086e814)
Visual Studio extension to enable Xamarin Designer tools in Visual Studio.

Xamarin Templates   16.1.47 (31f664d)
Templates for building iOS, Android, and Windows apps with Xamarin and Xamarin.Forms.

Xamarin.Android SDK   9.2.0.5 (HEAD/292d27fa)
Xamarin.Android Reference Assemblies and MSBuild support.
    Mono: mono/mono/2018-08-rc@5ad371dab1b
    Java.Interop: xamarin/java.interop/d16-0@c987483
    LibZipSharp: grendello/LibZipSharp/master@44de300
    LibZip: nih-at/libzip/rel-1-5-1@b95cf3f
    MXE: xamarin/mxe/xamarin@b9cbb535
    ProGuard: xamarin/proguard/master@905836d
    SQLite: xamarin/sqlite/3.26.0@325e91a
    Xamarin.Android Tools: xamarin/xamarin-android-tools/d16-0@0a7edd6


Xamarin.iOS and Xamarin.Mac SDK   12.8.0.0 (0aa8452)
Xamarin.iOS and Xamarin.Mac Reference Assemblies and MSBuild support.

[grendello]

I was able to reproduce this issue with the current stable version of XA on mac:

/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Android/Xamarin.Android.Common.targets(1930,2): error : Exception while loading assemblies: Java.Interop.Tools.Diagnostics.XamarinAndroidException: error XA0009: Error while loading assembly: /Users/grendel/.nuget/packages/system.runtime.loader/4.3.0/lib/MonoAndroid10/_._ ---> System.BadImageFormatException: Format of the executable (.exe) or library (.dll) is invalid. [/Users/grendel/Projects/xamarin/XamarianNugetReferenceErrorExample/TestApp/TestApp.csproj]
/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Android/Xamarin.Android.Common.targets(1930,2): error :   at Mono.Cecil.PE.ImageReader.ReadImage () [0x0001a] in <ace41b32821b47c593c4a9079c205dc8>:0  [/Users/grendel/Projects/xamarin/XamarianNugetReferenceErrorExample/TestApp/TestApp.csproj]
/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Android/Xamarin.Android.Common.targets(1930,2): error :   at Mono.Cecil.PE.ImageReader.ReadImage (Mono.Disposable`1[T] stream, System.String file_name) [0x0000a] in <ace41b32821b47c593c4a9079c205dc8>:0  [/Users/grendel/Projects/xamarin/XamarianNugetReferenceErrorExample/TestApp/TestApp.csproj]
/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Android/Xamarin.Android.Common.targets(1930,2): error :   at Mono.Cecil.ModuleDefinition.ReadModule (Mono.Disposable`1[T] stream, System.String fileName, Mono.Cecil.ReaderParameters parameters) [0x00008] in <ace41b32821b47c593c4a9079c205dc8>:0
/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Android/Xamarin.Android.Common.targets(1930,2): error :   at Mono.Cecil.ModuleDefinition.ReadModule (System.String fileName, Mono.Cecil.ReaderParameters parameters) [0x00078] in <ace41b32821b47c593c4a9079c205dc8>:0
/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Android/Xamarin.Android.Common.targets(1930,2): error :   at Mono.Cecil.AssemblyDefinition.ReadAssembly (System.String fileName, Mono.Cecil.ReaderParameters parameters) [0x00001] in <ace41b32821b47c593c4a9079c205dc8>:0
/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Android/Xamarin.Android.Common.targets(1930,2): error :   at Java.Interop.Tools.Cecil.DirectoryAssemblyResolver.ReadAssembly (System.String file) [0x00123] in <64394348237f4a4e87bcefbac87c92b2>:0
/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Android/Xamarin.Android.Common.targets(1930,2): error :   at Java.Interop.Tools.Cecil.DirectoryAssemblyResolver.Load (System.String fileName, System.Boolean forceLoad) [0x00029] in <64394348237f4a4e87bcefbac87c92b2>:0
/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Android/Xamarin.Android.Common.targets(1930,2): error :    --- End of inner exception stack trace ---
/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Android/Xamarin.Android.Common.targets(1930,2): error :   at Java.Interop.Tools.Diagnostics.Diagnostic.Error (System.Int32 code, System.Exception innerException, System.String message, System.Object[] args) [0x00009] in <6107c89312b54fce9fea76220443cab0>:0
/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Android/Xamarin.Android.Common.targets(1930,2): error :   at Java.Interop.Tools.Cecil.DirectoryAssemblyResolver.Load (System.String fileName, System.Boolean forceLoad) [0x00034] in <64394348237f4a4e87bcefbac87c92b2>:0
/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Android/Xamarin.Android.Common.targets(1930,2): error :   at Xamarin.Android.Tasks.ResolveAssemblies.ResolveRuntimeAssemblyForReferenceAssembly (NuGet.ProjectModel.LockFile lockFile, Java.Interop.Tools.Cecil.DirectoryAssemblyResolver resolver, System.String assemblyPath) [0x0015b] in <f75400f667544646a4fe83f8dcfa565c>:0
/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Android/Xamarin.Android.Common.targets(1930,2): error :   at Xamarin.Android.Tasks.ResolveAssemblies.Execute (Java.Interop.Tools.Cecil.DirectoryAssemblyResolver resolver) [0x0011e] in <f75400f667544646a4fe83f8dcfa565c>:0

The project builds fine with XA/master

[brendanzagaeski]

There are a few parts to the story with the System.Runtime.Loader NuGet package. If you are looking to use the System.Runtime.Loader.AssemblyLoadContext APIs directly in a Xamarin.Android app, those APIs are not currently implemented for mobile platforms.

If you are instead aiming to use some features from a different NuGet package that depends on System.Runtime.Loader, then there is an upcoming change in the next preview release of Xamarin.Android that might let you use APIs you want. The caution is that the APIs that you use from the other NuGet package won't work if they need to use System.Runtime.Loader.AssemblyLoadContext at run time. But depending on the NuGet package, it's possible that only a small portion of the functionality depends on the AssemblyLoadContext APIs. For reference, the upcoming change is #2770, which was motivated by a report from Visual Studio Developer Community.

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