Xamarin Android linking cannot access file

Question

I have a Xamarin Android project that I am trying to use Sdk and User Assembly linking with.

If I set the Android project to Sdk Assembly Linking only, the APK is created and deployed successfully and works.

However, when I set Sdk and User Assembly linking, with no other changes, I get the following error only when I deploy. The solution builds successfully.

The "LinkAssemblies" task failed unexpectedly.    
System.IO.IOException: The process cannot access the file '<path-to-project>\AppName\AppName.Android\obj\Release\android\assets\AppName.Core.dll' because it is being used by another process.
    at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
    at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost)
    at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share)
    at Mono.Cecil.ModuleDefinition.Write(String fileName, WriterParameters parameters)
    at Mono.Linker.Steps.OutputStep.WriteAssembly(AssemblyDefinition assembly, String directory)
    at Mono.Linker.Steps.OutputStep.OutputAssembly(AssemblyDefinition assembly)
    at Mono.Linker.Steps.OutputStep.ProcessAssembly(AssemblyDefinition assembly)
    at Mono.Linker.Steps.BaseStep.Process(LinkContext context)
    at Mono.Linker.Pipeline.Process(LinkContext context)
    at MonoDroid.Tuner.Linker.Process(LinkerOptions options, LinkContext& context)
    at Xamarin.Android.Tasks.LinkAssemblies.Execute(DirectoryAssemblyResolver res)
    at Xamarin.Android.Tasks.LinkAssemblies.Execute()
    at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute()
    at Microsoft.Build.BackEnd.TaskBuilder.<ExecuteInstantiatedTask>d__26.MoveNext()

AppName.Core.dll is another library project in my solution that is set to build as NetStandard 2.0.

I have looked through many other bug reports and forum posts regarding a similar issue to this, but most seem related to an earlier bug with Visual Studio 15.5.1 that has since been fixed.

The main Xamarin bug report is: https://bugzilla.xamarin.com/show_bug.cgi?id=56275 but was resolved in VS 15.2.
A forum topic (https://forums.xamarin.com/discussion/32976/updating-xamarin-broke-the-build-process-the-process-cannot-access-the-file-appname-dll-mdb) also talks about a similar issue being resolved in VS 15.5.1.
Other SO questions refer to older Xamarin or VS versions, or have unacceptable solutions (such as just turning off linking):
- The Link Assemblies tasks failed unexpectedly Xamarin Forms

Regardless, I have tried just about every solution suggested in those links including:

closing and reopening Visual Studio
deleting /bin and /obj folders
opening Visual Studio as Administrator
running MsBuild from a command prompt with VS closed

As well as various combinations of the above.

My custom linker.xml contains an exception for my library project:

<?xml version="1.0" encoding="utf-8" ?>
<linker>    
    ...    
    <assembly fullname="AppName.Core" ></assembly>        
    ...        
</linker>

At this point, I seem to have exhausted all available options and am no closer to a workable solution. Suggestions on solutions, workarounds, or other debugging paths to follow would be most appreciated.

My Android Options config:

Version Information:

Visual Studio Version: 15.5.6
Xamarin Forms Version: 2.5.0.280555
Xamarin Version: 26.1.0.1

dit you try removing Multi-dex or/and proguard from your configuration ? Something it not works with different linking other than the default one — OrcusZ, Mar 21 '18 at 08:17
@OrcusZ we require both Multi-dex and Proguard to be enabled. — Steve, Mar 21 '18 at 08:23
Can you just try to know if the issue comes from this options or not ? Furthermore the official documentation about linker from MS : https://learn.microsoft.com/en-us/xamarin/cross-platform/deploy-test/linker — OrcusZ, Mar 21 '18 at 09:55
@OrcusZ I tried turning off both Proguard and Multidex and got the same result. — Steve, Mar 22 '18 at 00:25
Maybe the obvious question, but did you report a bug on this yet? Stack Overflow isn't the best place to get **answers about potential bugs**. File a bug in the repository directly. https://github.com/xamarin/xamarin-android/issues/new — Jon Douglas, Mar 22 '18 at 02:19
@JonDouglas I'm trying to work out if it is a bug first. There doesn't seem to be anything substantially strange about my setup and I can't find anyone else having a similar issue, leading me to think it's something I'm doing. — Steve, Mar 22 '18 at 02:23
@Steve Based on everything you've written thus far, I would suspect a bug involving a file locking scenario. Definitely would be better filed as a bug to be looked at sooner than later. Also hopefully to not waste anymore of your time in the light it's a bug. — Jon Douglas, Mar 22 '18 at 02:31

score 1 · Answer 1 · answered Mar 27 '18 at 08:24

Please refer this link :

https://forums.xamarin.com/discussion/32976/updating-xamarin-broke-the-build-process-the-process-cannot-access-the-file-appname-dll-mdb

There are two solutions :

Close Visual Studio
deleting all the files in the bin\Debug folder
delete the .suo file
open Visual Studio in Administrator mode

If you have Xamarin Studio try this :

Open the solution in XamarinStudio and deploy it to the Android phone
Close the XamarinStudio
Open the solution in VisualStudio and deploy it to Android Phone

Hope this helps!!

I specifically link that thread in my question and explained I have already tried those basic steps. — Steve, Mar 27 '18 at 11:57

Xamarin Android linking cannot access file

1 Answers1