Diagnose Fast Deployment Issues

There are numerous situations where fast deployment does not work or gives an error. These normally end up displaying the following error

error XA0129: Error deploying 'files/.__override__/Foo.dll'.
/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Android/Xamarin.Android.Common.Debugging.targets(613,5): error XA0129: Please set the 'EmbedAssembliesIntoApk' MSBuild property to 'true' to disable Fast Deployment in the Visual Studio project property pages, or edit the project file in a text editor.

The general advice is to disable fast deployment by setting EmbedAssembliesIntoApk to true. This will allow the project to debug on the device. It does unblock the user but it does degrade the overally debug experience.

Given the numerous types of android devices out there, and the ability for the manufactures to alter the OS it is difficult to know what causes these issues allot of the time. So if you want to help us diagnose the issue here are a few steps which will help the team get to the bottom of what is causing the problem.

The Command Line

The first step is to try to reproduce the problem from the command line. Open a Developer Command Prompt for your IDE then navigate to the location of your Android csproj. Now depending on if you are using dotnet or Xamarin Classic will change how you install the project.

If you are using .NET 6+ for Android you can use the dotnet command to install your app.

dotnet build foo.csproj -t:Install -p:_FastDeploymentDiagnosticLogging=true -p:EmbedAssembliesIntoApk=false -bl

If you are still using the older style projects (Xamarin Classic) you can use msbuild.

msbuild foo.csproj -t:Install -p:_FastDeploymentDiagnosticLogging=true -p:EmbedAssembliesIntoApk=false -bl

Note we are passing an additional property _FastDeploymentDiagnosticLogging. This property enables some detailed diagnostic logging specifically for fast deployment. It is not on by default because it SLOWS down the deployment process. We are setting -p:EmbedAssembliesIntoApk=false to make use that fast deployment is turned on. The -bl will force dotnet or msbuild to produce a msbuild.binlog file which will contain the logs. This file can be zipped up and sent to use for analysis.

The IDE

If you are unable to reproduce the issue on the command line you will need to try to gather the required data from the IDE. The easiest way to do this is with the Project System Tools. Once installed it gives you access to all of the build logs for every build and saves then in binlog format as well. It is much more useful that the typical Diagnostic Text Logging provided by Visual Studio by default.

Project System Tools

Head to the following URL to install the extension Project System Tools 2022.

For details on how to use the extension see HowTo.

Build Settings

First thing to do is to re-enable fast deployment in the IDE by setting EmbedAssembliesIntoApk to false in the csproj or unchecking the appropriate check box in the project properties. This will make sure fast deployment is being used. It is very easy to forget this step as the error message does tell you to disable it.

In order to get the additional diagnostic data in the IDE we need to set the _FastDeploymentDiagnosticLogging for the build. The easiest way is to add the following xml snippet to your csproj.

<PropertyGroup>
   <_FastDeploymentDiagnosticLogging>true</_FastDeploymentDiagnosticLogging>
</PropertyGroup>

You can add this anywhere in between the Project elements in the csproj.

Alternatively if you do not want to edit your csproj you can create a Directory.Build.props file in the same directory and paste in the following contents.

<Project>
<PropertyGroup>
   <_FastDeploymentDiagnosticLogging>true</_FastDeploymentDiagnosticLogging>
</PropertyGroup>
</Project>

If you already use a Directory.Build.props you can add the PropertyGroup contents to that existing file.

Gathering the Data

Once you have Project System Tools installed and the _FastDeploymentDiagnosticLogging property set you can start gathering the diagnostic data. Follow the instructions here to open the Project System Tools window in Visual Studio. You can then click the "play" button to start logging.

Then deploy your application. The various builds will appear in the list. You are speficially looking for the one which calls the Install or _Run targets. Right click and save these logs to a location of your choice. Then zip these up and send them to the team.

Note that the additional logging WILL slow down deployment times and it does produce ALLOT of data. So deployment times will be slower, we do NOT recommend you leave the _FastDeploymentDiagnosticLogging on all the time. It is only for gathering data.