How to use "InternalsVisibleTo" attribute with Strongly named assembly?

c# .net-assembly
Dave picture Dave · Jun 19, 2015 · Viewed 26k times · Source

I am using the "InternalsVisibleTo" attribute with an assembly to expose the internal methods/classes to my unit test project.

I now need to install that assembly into the GAC, so I need to give it a strong name. When I try doing that, I get the following error in Visual Studio.

Strong-name signed assemblies must specify a public key in their InternalsVisibleTo declarations

A bit of Googling brought me to the article below:

https://msdn.microsoft.com/en-us/library/bb763089.aspx

This article states:

"Determine the public key for the strong-named friend assembly."

This article does not say how to determine the public key. Where do I find the public key for the assembly? Also, once I have the public key, would this be the correct way to declare the attribute? 

[assembly: InternalsVisibleTo("Namespace.Assembly.Example.Name, PublicKey=ThePublicKey")]

Answer

Invvard picture Invvard · Oct 11, 2017

UPDATE May 2019 : It works perfectly with Visual Studio 2019.

To anyone that is using Visual Studio 2017, there is the latest method :

From our beloved IDE, go to "Tools > External Tools..." and "Add" a new tool with those settings :

  • Title : Get PublicKey
  • Command : "C:\Program Files (x86)\Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.6.2 Tools\sn.exe" (/!\ choose the NETFX tool version that match your assembly NETFX version, here it's 4.6.2)
  • Arguments : -Tp $(TargetPath)
  • Check the "Use Output window" checkbox

Apply/OK those changes.

In the "Solution explorer" click on your project assembly name, and then head to "Tools > Get PublicKey". The Output window should display the (quite long) Public Key, along with the Public Token Key.

Finally, in the project that holds the internal class (i.e. the tested project) you want to expose, open the "AssemblyInfo.cs" file and add the line :

[assembly: InternalsVisibleTo("MyCompany.SolutionName.ProjectName, PublicKey=Paste your public key here")]

/!\ You have to remove the line breaks from your public key.

It worked perfectly for me, so hopefully it'll do the trick for you as well !

Related questions

System.IO.FileNotFoundException: Could not load file or assembly 'X' or one of its dependencies when deploying the application

I'm having a strange problem with deploying an application, which references an assembly, written in managed c++. I've created an assembly X, compiled it and referenced it in an exe file, called Starter. Starter.exe starts normally on local mashine. …

Read More
How can I get the executing assembly version?

I am trying to get the executing assembly version in C# 3.0 using the following code: var assemblyFullName = Assembly.GetExecutingAssembly().FullName; var version = assemblyFullName .Split(',')[1].Split('=')[1]; Is there another proper way of doing so?

Read More
No assembly found containing an OwinStartupAttribute Error

This error The following errors occurred while attempting to load the app. - No assembly found containing an OwinStartupAttribute. - The given type or method 'false' was not found. Try specifying the Assembly. To disable OWIN startup discovery, add the …

Read More