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NuSpec Reference Generator


Package authoring for .NET Core based libraries (ASPNET Core 1.0, CoreCLR, UWP) has an extra burden on the author as .NET dependencies must be listed in addition to any regular packages you depend on. This could be a long list and it's a challenge to get it right. If you use any of the meta-packages that brings "all" of .NET Core into your project as possible references, how do you know which you actually need?

This tool aims to help by reading your compiled libraries assembly metadata and determine what that list should be. It currently supports any System.Runtime based project, including "Profile 259"+ PCL's -- that is, a PCL that targets at least .NET 4.5, Windows 8 and Windows Phone 8.

Build Status

Branch Status
master Build status


This tool uses some conventions to locate your nuspec file and input libraries. These can be overridden in your project file. The tool looks for a .nuspec file with the same name as your target library underneath the solution root directory. By default, it will add/update a <dependencies> group for the dotnet TFM, but you can have it generate others by overriding your project file value.

Using NuGet, add NuSpec.ReferenceGenerator to your library project. On build, it will add/update your nuspec with the correct dependency data for your libraries.

If you have existing package dependencies in your nuspec in the group that aren't picked up by this tool, they'll be silently ignored. This could happen in the case where a HintPath to a Package is missing and the package could not be detected.

When you author your nuspec package, make sure that your library goes into the \lib\netstandard1.x directory, where x depends on your library. PCL 259's are all netstandard1.0.

Packages containing netstandard and existing libraries

If you have a package that contains a netstandard group and your users use packages.config, you may want to add blank dependency groups. Note that Xamarin Studio 6.1, currently in the alpha channel, supports project.json and that is the recommended solution.

<group targetFramework="net45" />
<group targetFramework="wp8" />
<group targetFramework="win8" />
<group targetFramework="wpa81" />
<group targetFramework="xamarin.ios" />
<group targetFramework="monotouch" />
<group targetFramework="monoandroid" />

Depending on the minimum platform versions you target and the minimum platforms supported by your netstandard1.x dependencies. NuGet will evaluate netstandard1.x for any "System.Runtime" based platform, so that effectively means, net45, wp8, win8, wpa81, xamarin.ios, monotouch, and monoandroid. Those platforms support System.Runtime 4.0.0. If you target a newer set of platforms, like net451, Win81 and wpa81 (Profile 151), then it's System.Runtime is 4.0.10.

For example, if you're putting a Profile 151 library in netstandard1.1, then your System.Runtime is 4.0.10 and will run on .NET 4.5.1 and higher. For older platforms like .NET 4.5, you'll need to add a blank group

<group targetFramework="net45" />

to ensure that those older platforms don't try to add references to the newer dependencies specified in your netstandard section.

To sum this up, look at the output of the tool for the netstandard section. If you have a System.Runtime higher than 4.0.0, and you want to to target net45, wp8, win8, xamarin.ios, monotouch, or monoandroid, then you need to block the netstandard dependency group by adding blank dependency groups for the other platforms.

Options and overriding default behavior

NuSpec Library Content The library files that should be checked for dependencies. Most packages should have a single assembly which the tool will detect. If you have more than one file packaged in your nupkg, then you need to to specify the following in your csproj/vbproj file. You'll also need to specify the project file for it in the next section:

  <!-- output of this project -->
  <NuSpecLibContent Include="$(TargetPath)">

  <!-- another library we're distributing in the same nupkg -->
  <NuSpecLibContent Include="$(TargetDir)AnotherLibrary.dll">

NuSpec Project Files The library files that should be checked for dependencies. Most packages should have a single assembly which the tool will detect. If you have more than one file packaged in your nupkg, then you need to to specify the following in your csproj/vbproj file:

  <!-- this project -->
  <NuSpecProjectFile Include="$(MSBuildThisFileFullPath)">

  <!-- another library we're distributing in the same nupkg -->
  <!-- Note: Order matters here; use the same order as for NuSpecLibContent -->
  <NuSpecProjectFile Include="$(SolutionDir)AnotherLibrary\AnotherLibrary.csproj">

NuSpec File By default, the tool will look for a .nuspec file with the same name as your library underneath your solution directory, recursively. If your .nuspec has a different filename, then you need to specify it in your csproj/vbproj file:

  <!-- example NuSpec file that must be specified -->
  <NuSpecFile Include="$(SolutionDir)package\.nuspec">

Target Frameworks By default, the tool will add/update a dependency group for the netstandard1.x TFM for a PCL or uap10.0 for a UWP Class Library. In some cases, you may need to have multiple dependency groups, like having both netstandard1.x and uap10.0. An example of this is if your package includes a win8 or win81 library but you'd like the .NET Core-based one to be used there. netstandard1.x isn't enough as win81 is more specific and would "win." Instead, just copy your netstandard1.x library to also be under \lib\uap10.0 and specify an additional TFM for the tool to add/update. This should be a semi-colon joined list.

<!-- netstandard1.x and uap10.0 tfms -->

Command line (2.0)

This tool is a command line that you can call in other ways. The command line exposes additional features targeted at NuGet packages containing cross-compiled libraries. The general syntax for the command line is: RefGen.exe command options. All of the options are required for each command but the order doesn't matter.

There are two commands

Command Description
generate-single Single library wtih a fixed set of functionality (eg. PCL 259 or netstandard1.0). Usable with csproj/vbproj-based projects that use either packages.config or project.json for their packages
generate-cross Library that's cross-compiled enabling more functionality on newer platforms (eg. netstandard1.0 and netstandard1.3). Only usable with xproj-based project that use project.json for cross-compiling to several target frameworks

generate-single options

This is the same functionality that RefGen 1.0 had, extended with support for .NET Standard.

Switch Description
-m or --moniker NuGetTargetMonikers -- .NETStandard,Version=v1.4
-t or --tfm TFM's to generate, semi-colon joined. E.g.: auto;uap10.0
-n or --nuspec Full path to NuSpec file
-p or --project Full path to project file (csproj/vbproj)
-f or --file Full path target files, semi-colon joined

generate-cross options

This functionality is new in version 2.0 and enables the use of xproj/project.json-based cross-compiling projects. It requires use a NuSpec file as calling dotnet pack project.json doesn't provide a way of trimming the dependencies list.

In this model, you'd typically have a project.json dependency on NETStandard.Library. The issue is that when creating your NuPkg, it's better to list the individual dependencies you require instead of a giant meta-package. This RefGen tool enables this scenario.

Switch Description
-p or --project Full path to project file (project.json)
-d or --directory Path to base directory where the output folders are created per target framework). The output would be in <directory>\netstandard1.0\MyLib.dll for example.
-n or --nuspec Full path to the nuspec file
-l or --library Library name, including .dll. MyLibrary.dll, for example

Upgrading from 1.x

The 2.0 version will detect/use the 1.x command line options. Updating should not break your scripts.

Command line (1.x)

This tool is a command line that you can call in other ways. The parameters are as follows and they are all required:

// args 0: NuGetTargetMoniker: .NETPlatform,Version=v5.0
// args 1: TFM's to generate, semi-colon joined. E.g.: auto;uap10.0
// args 2: nuspec file, full path
// args 3: project file (csproj/vbproj, etc) full path. Used to look for packages.config/project.json and references. should match order of target files
// args 4: target files, semi-colon joined, full path


  • This tool does not currently run on mono if you're using an "classic PCL". The tool needs all of the PCL contracts from the Reference Assemblies folder for comparison; if there's an equiv on Mono, then this could be fixed. Alternatively, if you only need project.json based projects, then there's no limitation.


  • 2.0.0-beta-bld12: Support for cross-compiled xproj. Updated command line options
  • 2.0.0-beta1: Initial support for netstandard and .NET Core RC2
  • 1.4.2: Add a more descriptive error message for NuSpec files that have incorrect XML namespace declarations
  • 1.4.1: Issue warning and do not run RefGen on non-Windows systems until full mono compatibility is tested and verified. Prevents breaking builds.
  • 1.4: Fix issue where BCL libs weren't detected correctly for PCL projects using project.json instead of packages.config
  • 1.3.6: Fix TFM version parsing when running on cultures that use , instead of . (#14)
  • 1.3.5: Fix for pre-release number parsing so that it can work with a "number" group that is larger than int.MaxValue (#13)
  • 1.3.4: Set developmentDependency=true to prevent NuSpec.ReferenceGenerator from being seen a runtime dependency
  • 1.3.3: Add backslash to NuSpecFile search path when SolutionDir isn't defined, don't define SolutionDir if it's not already defined
  • 1.3.2: Check for blank $(SolutionDir) and default to parent directory of project
  • 1.3.1: Set default TFM for UWP class libraries to uap10.0
  • 1.3: Fix bug when using with UWP class libraries. Also include support for projectName.project.json added in NuGet 3.2.
  • 1.2: Prevent included items (nuspec, project files, libraries) from showing up in Visual Studio. Changed NuSpecTfm to a PropertyGroup from an ItemGroup.
  • If you were setting NuSpecTfm you'll need to update your settings to use PropertyGroup for that item.
  • 1.0.1: Add Portable- to ensure the package works for packages.config based projects.
  • 1.0: Initial Release


If you find any issues, please open an issue in the tracker and/or ping me (@onovotny) on Twitter and I'll try to help.


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