Is NuGet metapackage reserved to .net core only?

Question

In the .NET doc, I see a lot of explanations around nuget metapackages, bu all the samples are with .NET Core. Is it possible to create metapackage for full .net framework assemblies and consume this with a .net framework app?

Will it be possible only with ProjectReference and not with packages.config?

Thanks!

Answer 1

A metapackage is just a package that doesn't contain any content/libraries of its own and has dependencies to all the other packages that it encompasses. This isn't something specific to NuGet, by the way, many package managers have the same concept and usually call them meta packages too.

About NuGet specifically, since NuGet has to deal with different target frameworks and asset selection, which many package managers don't have to worry about, it might be necessary to put some fake information in the nupkg to make it work properly. What I think I've seen before is to create an empty file named _._ in the lib\\target framework folders that match the TFMs that the dependant packages use. For example, if you create a metapackage for packages that have libs for net45 and netstandard2.0, then you'd have two files in the nupkg, lib/net45/_._ and lib/netstandard2.0/_._ , both are empty. However, I haven't tested this myself, so you should, but just in case a nupkg with only a nuspec and nothing else doesn't work, try this.

Since meta packages aren't otherwise special (they have the same package type as "regular" packages), they work just fine with both packages.config and PackageReference. Meta packages are perhaps most useful for PackageReference, because it supports transitive dependencies. In other words, the user adds the metapackage, their csproj gets one reference and is otherwise "clean". With packages.config, when they add the metapackage, all of the transitive dependencies will also get added to packages.config and csproj.