Xamarin Android App Project Building Issue after Visual Studio 2017 Update to 15.8.1/15.8.2

Question

After the upgrade of Visual Studio 2017 to 15.8.1 and with the Android SDK version 28 (supporting Android 9.0 P), we are facing issue in building our Xamarin based Android App C# project with the below error:

_LinkAssembliesNoShrink:
  Creating "obj\\ObRelease\MonoAndroid90\link.flag" because "AlwaysCreate" was specified.
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning : Failed to read 'D:\MyAndroidApp\obj\ObRelease\MonoAndroid90\android\assets\Mono.Android.dll' with debugging symbols. Retrying to load it without it. Error details are logged below. [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning : Mono.Cecil.Cil.SymbolsNotMatchingException: Symbols were found but are not matching the assembly [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Mono.Cecil.ModuleDefinition.ReadSymbols(ISymbolReader reader, Boolean throwIfSymbolsAreNotMaching) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Mono.Cecil.ModuleReader.ReadSymbols(ModuleDefinition module, ReaderParameters parameters) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Mono.Cecil.ModuleReader.CreateModule(Image image, ReaderParameters parameters) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Mono.Cecil.ModuleDefinition.ReadModule(Disposable`1 stream, String fileName, ReaderParameters parameters) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Mono.Cecil.ModuleDefinition.ReadModule(String fileName, ReaderParameters parameters) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Mono.Cecil.AssemblyDefinition.ReadAssembly(String fileName, ReaderParameters parameters) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Java.Interop.Tools.Cecil.DirectoryAssemblyResolver.ReadAssembly(String file) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning : Failed to read 'D:\MyAndroidApp\obj\ObRelease\MonoAndroid90\android\assets\System.dll' with debugging symbols. Retrying to load it without it. Error details are logged below. [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning : Mono.Cecil.Cil.SymbolsNotMatchingException: Symbols were found but are not matching the assembly [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Mono.Cecil.ModuleDefinition.ReadSymbols(ISymbolReader reader, Boolean throwIfSymbolsAreNotMaching) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Mono.Cecil.ModuleReader.ReadSymbols(ModuleDefinition module, ReaderParameters parameters) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Mono.Cecil.ModuleReader.CreateModule(Image image, ReaderParameters parameters) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Mono.Cecil.ModuleDefinition.ReadModule(Disposable`1 stream, String fileName, ReaderParameters parameters) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Mono.Cecil.ModuleDefinition.ReadModule(String fileName, ReaderParameters parameters) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Mono.Cecil.AssemblyDefinition.ReadAssembly(String fileName, ReaderParameters parameters) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Java.Interop.Tools.Cecil.DirectoryAssemblyResolver.ReadAssembly(String file) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning : Failed to read 'D:\MyAndroidApp\obj\ObRelease\MonoAndroid90\android\assets\System.Xml.dll' with debugging symbols. Retrying to load it without it. Error details are logged below. [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning : Mono.Cecil.Cil.SymbolsNotMatchingException: Symbols were found but are not matching the assembly [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Mono.Cecil.ModuleDefinition.ReadSymbols(ISymbolReader reader, Boolean throwIfSymbolsAreNotMaching) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Mono.Cecil.ModuleReader.ReadSymbols(ModuleDefinition module, ReaderParameters parameters) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Mono.Cecil.ModuleReader.CreateModule(Image image, ReaderParameters parameters) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Mono.Cecil.ModuleDefinition.ReadModule(Disposable`1 stream, String fileName, ReaderParameters parameters) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Mono.Cecil.ModuleDefinition.ReadModule(String fileName, ReaderParameters parameters) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Mono.Cecil.AssemblyDefinition.ReadAssembly(String fileName, ReaderParameters parameters) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): warning :    at Java.Interop.Tools.Cecil.DirectoryAssemblyResolver.ReadAssembly(String file) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): error MSB4018: The "GenerateJavaStubs" task failed unexpectedly. [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): error MSB4018: System.NullReferenceException: Object reference not set to an instance of an object. [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): error MSB4018:    at Java.Interop.Tools.TypeNameMappings.JavaNativeTypeManager.<>c.<ToJniNameFromAttributes>b__42_0(CustomAttribute a) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): error MSB4018:    at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext() [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): error MSB4018:    at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source, Func`2 predicate) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): error MSB4018:    at Java.Interop.Tools.TypeNameMappings.JavaNativeTypeManager.ToJniNameFromAttributes(TypeDefinition type) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): error MSB4018:    at Java.Interop.Tools.TypeNameMappings.JavaNativeTypeManager.ToJniName[T](T type, Func`2 decl, Func`2 name, Func`2 ns, Func`2 overrideName, Func`2 shouldUpdateName) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): error MSB4018:    at Java.Interop.Tools.TypeNameMappings.JavaNativeTypeManager.ToJniName(TypeDefinition type, ExportParameterKind exportKind) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): error MSB4018:    at Java.Interop.Tools.TypeNameMappings.JavaNativeTypeManager.ToJniName(TypeDefinition type) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): error MSB4018:    at Java.Interop.Tools.JavaCallableWrappers.TypeNameMapGenerator.GetTypeMapping(Func`2 skipType, Func`2 key, Func`2 value) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): error MSB4018:    at Java.Interop.Tools.JavaCallableWrappers.TypeNameMapGenerator.WriteJavaToManaged(Stream output) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): error MSB4018:    at Xamarin.Android.Tasks.GenerateJavaStubs.UpdateWhenChanged(String path, Action`1 generator) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): error MSB4018:    at Xamarin.Android.Tasks.GenerateJavaStubs.WriteTypeMappings(List`1 types) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): error MSB4018:    at Xamarin.Android.Tasks.GenerateJavaStubs.Run(DirectoryAssemblyResolver res) [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): error MSB4018:    at Xamarin.Android.Tasks.GenerateJavaStubs.Execute() [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): error MSB4018:    at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute() [D:\MyAndroidApp.csproj]
C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\Xamarin\Android\Xamarin.Android.Common.targets(2153,3): error MSB4018:    at Microsoft.Build.BackEnd.TaskBuilder.<ExecuteInstantiatedTask>d__26.MoveNext() [D:\MyAndroidApp.csproj]
Done Building Project "D:\MyAndroidApp.csproj" (default targets) -- FAILED.

Any clues OR any solutions OR any workarounds?

UPDATE: Even after the update of Visual Studio 2017 to 15.8.2, the issue is still there.

Answer 1

Not an expert on Xamarin Android projects but wanted to just give few suggestions:

1. According to this old bug, this might have happened due to dangling references. So check your references, clean your project, manually clean output (Release/Debug) folders and try building project again.
2. According to error message, error is coming from ToJniNameFromAttributes method in this file. So better check reference to Java.interop package.
3. Lastly, you can create a new Xamarin Android app and then compare project configuration files (csproj file, unload the project and right click in solution explorer to edit csproj file) from both working and not working project side by side to hunt the problematic project configuration down.

Hope this helps a bit!

Issue Specific Answer :

Below is the project reference changes I had done to solve the issue specifically. Just adding it here as it can be more helpful for someone reading the answer to understand the issue\\solution.

Original references were as below:

<Reference Include="Mono.Android, Version=0.0.0.0, Culture=neutral, PublicKeyToken=84e04ff9cfb79065, processorArchitecture=MSIL">
  <SpecificVersion>False</SpecificVersion>
</Reference>
<Reference Include="Mono.Android.Export, Version=0.0.0.0, Culture=neutral, PublicKeyToken=84e04ff9cfb79065, processorArchitecture=MSIL">
  <SpecificVersion>False</SpecificVersion>
</Reference>
<Reference Include="mscorlib">
  <Private>False</Private>
</Reference>
<Reference Include="System, Version=2.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e, processorArchitecture=MSIL">
  <SpecificVersion>False</SpecificVersion>
</Reference>
<Reference Include="System.Core" />
<Reference Include="System.Xml, Version=2.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e, processorArchitecture=MSIL">
  <SpecificVersion>False</SpecificVersion>
</Reference>

Reference after the changes (with which the build passed):

<Reference Include="Mono.Android" />
<Reference Include="Mono.Android.Export" />
<Reference Include="mscorlib" />
<Reference Include="System" />
<Reference Include="System.Core" />
<Reference Include="System.Xml" />