Output items from msbuild custom target - msbuild

Question

After spending the whole day studying MsBuild: project files, items, properties, targets and tasks, I still cannot find a solution for my problem.
I aim to create a custom target in my .csproj to generate binary files from input text files using console program. The target does what it should do. But I want the generated files to be part of the project file as Content that should be copied (published) together with an application.
I ended up the the following project file:
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<TargetFrameworks>netstandard2.0</TargetFrameworks>
</PropertyGroup>
<PropertyGroup>
<MyTool>.\tools\mytool.exe</MyTool>
</PropertyGroup>
<Target Name="MyTarget" DependsOnTargets="Restore" BeforeTargets="Build;Publish"
Inputs="#(TxtFiles)"
Outputs="#(TxtFiles->'%(RootDir)%(Directory)%(Filename).bin')">
<Exec Command="$(MyTool) -o %(TxtFiles.RootDir)%(TxtFiles.Directory)%(TxtFiles.Filename).bin %(TxtFiles.Identity)"
Outputs="#(TxtFiles->'%(RootDir)%(Directory)%(Filename).bin')">
<Output TaskParameter="Outputs" ItemName="BinFiles" />
</Exec>
</Target>
<ItemGroup>
<TxtFiles Include="my_resources\*.txt" />
<Content Include="#(TxtFiles)">
<CopyToOutputDirectory>Never</CopyToOutputDirectory>
</Content>
<Content Include="#(BinFiles)">
<CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
<PublishState>Included</PublishState>
</Content>
</ItemGroup>
</Project>
Unfortunately - it doesn't populate item #(BinFiles).
If if declate it manually (as if calling the tool beforehand), it works:
<ItemGroup>
<Content Include="my_resources\*.bin">
<CopyToOutputDirectory>Always</CopyToOutputDirectory>
<PublishState>Included</PublishState>
</Content>
</ItemGroup>
I want to achieve the same behavior. Also as my target declares inputs and outputs, how whould it populate its outputs to be added as content?

Answer 1

Finally, the other question had a clue in the answer.
Using it managed to define the final project file which worked as intended. I understood that I do not need the target Outputs, but rather add them to the Contents item.
I ended up with the following:
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<TargetFrameworks>netstandard2.0</TargetFrameworks>
</PropertyGroup>
<PropertyGroup>
<MyTool>.\tools\mytool.exe</MyTool>
</PropertyGroup>
<ItemGroup>
<Content Include="my_resources\**\*.txt">
<CopyToOutputDirectory>Never</CopyToOutputDirectory>
</Content>
</ItemGroup>
<Target Name="MyTarget" DependsOnTargets="Restore" BeforeTargets="BeforeBuild;PrepareForPublish">
<ItemGroup>
<TxtFiles Include="#(Content)" Condition="'%(Extension)' == '.txt'" />
</ItemGroup>
<Exec Command="$(MyTool) -o $([System.IO.Path]::ChangeExtension('%(TxtFiles.Fullpath)','.bin')) %(TxtFiles.Identity)"
Outputs="$([System.IO.Path]::ChangeExtension('%(TxtFiles.Fullpath)','.bin'))">
<Output TaskParameter="Outputs" ItemName="_BinFiles" />
</Exec>
<ItemGroup>
<Content Include="#(_BinFiles)">
<CopyToOutputDirectory>Always</CopyToOutputDirectory>
<PublishState>Included</PublishState>
</Content>
<BinFiles Include="#(Content)" Condition="'%(Extension)' == '.bin'" />
</ItemGroup>
</Target>
</Project>