Xamarin Android - JsonSerializationException: Error getting value from '[FIELD]' on '[METHOD]' about xamarin-android

[radekdoulik]

I am unable to reproduce it. Tried it with XA Version: 8.1.0.22

If it still happens for you, please attach whole XA project, which reproduces the issue.

[lorisgiglio]

Hi, it's a big xamarin project with many references and I can't attach all the project.
I've same problem on Android 5.1 and Android 7.1 devices.

The problems seems to depend by dynamic method creation during NewtonSoft serialization but I don't know how it happens and why.

It happens in Release mode and not in Debug mode compilation. I saw that loaded assembly in debug mode are :

Loaded assembly: Microsoft.CSharp.dll [External]
Loaded assembly: System.ComponentModel.TypeConverter.dll [External]
Loaded assembly: Anonymously Hosted DynamicMethods Assembly [External]
Loaded assembly: System.Reflection.Primitives.dll [External]
Loaded assembly: System.Net.Http.dll [External]

My project can't compile in Release mode with Linking "SDK Assembly Only" but only with "NONE".

I attach all compile detailed debug information if it can help.
DEBUG_MODE.txt
RELEASE_MODE_LINKING_NONE.txt
RELEASE_MODE_LINKING_SDKASSEMBLYONLY.txt

[jonpryor]

From RELEASE_MODE_LINKING_SDKASSEMBLYONLY.txt

error MSB4018: errore imprevisto dell'attivit‡ "LinkAssemblies".
error MSB4018: System.NullReferenceException: Riferimento a un oggetto non impostato su un'istanza di oggetto.
error MSB4018:    in Mono.Linker.TypeReferenceExtensions.<GetMethods>d__4.MoveNext()
error MSB4018:    in Mono.Linker.Steps.TypeMapStep.TryMatchMethod(TypeReference type, MethodDefinition method)
error MSB4018:    in Mono.Linker.Steps.TypeMapStep.GetBaseMethodInTypeHierarchy(TypeDefinition type, MethodDefinition method)
error MSB4018:    in Mono.Linker.Steps.TypeMapStep.MapVirtualMethods(TypeDefinition type)
error MSB4018:    in Mono.Linker.Steps.TypeMapStep.MapType(TypeDefinition type)
error MSB4018:    in Mono.Linker.Steps.TypeMapStep.ProcessAssembly(AssemblyDefinition assembly)
error MSB4018:    in Mono.Linker.Steps.BaseStep.Process(LinkContext context)
error MSB4018:    in Mono.Linker.Pipeline.Process(LinkContext context)
error MSB4018:    in MonoDroid.Tuner.Linker.Process(LinkerOptions options, LinkContext& context)
error MSB4018:    in Xamarin.Android.Tasks.LinkAssemblies.Execute(DirectoryAssemblyResolver res)
error MSB4018:    in Xamarin.Android.Tasks.LinkAssemblies.Execute()
error MSB4018:    in Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute()
error MSB4018:    in Microsoft.Build.BackEnd.TaskBuilder.<ExecuteInstantiatedTask>d__26.MoveNext()

I suspect that you're hitting xamarin/xamarin-macios#3215, the fix for which involves a null check within TypeReferenceExtensions.GetMethods(), so I think that this is fixed in:

• dotnet/linker@c62335c (actual fix)
• mono/mono@3c3e692 (integrate above fix into mono)
• a82c286 (integrate mono fix into xamarin-android)

The fix has not yet been integrated on xamarin-android/master; the last URL above is on xamarin-android/d15-6, which is for Xamarin.Android 8.2 (currently in beta).

However, I don't know when that fix will actually be released.