How to declare a friend assembly?

c# visual-studio-2008 assembly-signing
Hemant picture Hemant · Jul 14, 2009 · Viewed 33.2k times · Source

I have 2 projects in my solution:

  1. Assembly (Basic Library)
  2. Test Assembly (NUnit)

I had declared the test assembly as friends assembly in first project:

[assembly: InternalsVisibleTo ("Company.Product.Tests")]

Everything was working fine till I realised that I have forgot to setup the solution to sign my assemblies. So created a snk file and setup the visual studio project to sign the first assembly (Basic Library). Now when I compile the first project, I get following error:

Friend assembly reference 'Company.Product.Tests' is invalid. Strong-name signed assemblies must specify a public key in their InternalsVisibleTo declarations.

I tried to extract the public key from my snk file using sn utility but it generates a wired binary file which I am unsure how to use. How can I fix the problem?

Answer

Jon Skeet picture Jon Skeet · Jul 14, 2009

You need to sign both assemblies, because effectively both assemblies reference each other.

You have to put the public key in the InternalsVisibleTo attribute. For example, in Protocol Buffers I use:

[assembly:InternalsVisibleTo("Google.ProtocolBuffers.Test,PublicKey="+
"00240000048000009400000006020000002400005253413100040000010001008179f2dd31a648"+
"2a2359dbe33e53701167a888e7c369a9ae3210b64f93861d8a7d286447e58bc167e3d99483beda"+
"72f738140072bb69990bc4f98a21365de2c105e848974a3d210e938b0a56103c0662901efd6b78"+
"0ee6dbe977923d46a8fda18fb25c65dd73b149a5cd9f3100668b56649932dadd8cf5be52eb1dce"+
"ad5cedbf")]

The public key is retrieved by running

sn -Tp path\to\test\assembly.dll

Alternatively, get it from the .snk file:

sn -p MyStrongnameKey.snk public.pk
sn -tp public.pk

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