NuGet package: Copy DLLs to subdirectories in buildoutput - nuget

Question

I want to create a NuGet package that copies the DLLs into a subdirectory of the output directory.
This is what the folder structure of my package looks like:
Package root
lib
net48
x64
First.dll
Second.dll
x86
First.dll
Second.dll
The DLLs should be copied to the respective subdirectory in the output folder as follows:
Output directory
x64
First.dll
Second.dll
x86
First.dll
Second.dll
I have tried the files attribute in the nuspec file:
<files>
<file src="lib\net48\amd64\*.dll" target="amd64\" />
<file src="lib\net48\x86\*.dll" target="x86\" />
</files>
When building the package the following warning appears for each DLL I use:
WARNING: NU5100: The assembly 'amd64\First.dll' is not inside
the 'lib' folder and hence it won't be added as a reference when the
package is installed into a project. Move it into the 'lib' folder if
it needs to be referenced.
Neither the subfolders are created nor the DLLs are copied into the output folder after I restored all packages.
How can I configure the nuspec file so that the DLLs are copied into the subfolders? Do I need an install.ps1 script?

Answer 1

I'm using .NET Core (and .NET 5) projects. And packaging one component with multiple project DLLs. Can do this by modifying prject files.
So if you also have .NET Core projects add the following section to your .csproj file (to the project which should be packaged) to package DLL, change the DLL names and path as you need it.
<ItemGroup>
<_PackageFiles Include="$(OutputPath)\First.dll">
<BuildAction>None</BuildAction>
<PackagePath>x64</PackagePath>
</_PackageFiles>
<_PackageFiles Include="$(OutputPath)\First.dll">
<BuildAction>None</BuildAction>
<PackagePath>x86</PackagePath>
</_PackageFiles>
</ItemGroup>