How to fix "Referenced assembly does not have a strong name" error

To avoid this error you could either:

• Load the assembly dynamically, or
• Sign the third-party assembly.

You will find instructions on signing third-party assemblies in .NET-fu: Signing an Unsigned Assembly (Without Delay Signing).

Signing Third-Party Assemblies

The basic principle to sign a thirp-party is to

1. Disassemble the assembly using ildasm.exe and save the intermediate language (IL):

   ildasm /all /out=thirdPartyLib.il thirdPartyLib.dll 
   

2. Rebuild and sign the assembly:

   ilasm /dll /key=myKey.snk thirdPartyLib.il
   

Fixing Additional References

The above steps work fine unless your third-party assembly (A.dll) references another library (B.dll) which also has to be signed. You can disassemble, rebuild and sign both A.dll and B.dll using the commands above, but at runtime, loading of B.dll will fail because A.dll was originally built with a reference to the unsigned version of B.dll.

The fix to this issue is to patch the IL file generated in step 1 above. You will need to add the public key token of B.dll to the reference. You get this token by calling

sn -Tp B.dll 

which will give you the following output:

Microsoft (R) .NET Framework Strong Name Utility  Version 4.0.30319.33440
Copyright (c) Microsoft Corporation.  All rights reserved.

Public key (hash algorithm: sha1):
002400000480000094000000060200000024000052534131000400000100010093d86f6656eed3
b62780466e6ba30fd15d69a3918e4bbd75d3e9ca8baa5641955c86251ce1e5a83857c7f49288eb
4a0093b20aa9c7faae5184770108d9515905ddd82222514921fa81fff2ea565ae0e98cf66d3758
cb8b22c8efd729821518a76427b7ca1c979caa2d78404da3d44592badc194d05bfdd29b9b8120c
78effe92

Public key token is a8a7ed7203d87bc9

The last line contains the public key token. You then have to search the IL of A.dll for the reference to B.dll and add the token as follows:

.assembly extern /*23000003*/ MyAssemblyName
{
  .publickeytoken = (A8 A7 ED 72 03 D8 7B C9 )                         
  .ver 10:0:0:0
}

For me, the problem was a NuGet package without a strong name. The solution was to install StrongNamer from NuGet, which automatically adds a strong name to all referenced assemblies. Just simply having it referenced in the project fixed my issue.

Use ilmerge. ilmerge is from Microsoft, but it is not shipped with Visual Studio or the SDKs. You can download it from here though. There is also a GitHub repository. You can also install from NuGet:

PM> Install-Package ilmerge

To use:

ilmerge assembly.dll /keyfile:key.snk /out:assembly.dll /targetplatform:v4,C:\Windows\Microsoft.NET\Framework\v4.0.30319 /ndebug

If needed, you can generate your own keyfile using sn (from Visual Studio):

sn -k key.snk

Situation: You had project A,B,C,D in solution X,Y

Project A, B, C in X Project A, C, D in Y

I need use project C in project A, but later i dont use. In bin Debug project A had C.dll.

If I compile solution X, all good ( in this solution i delete reference A -> C. ), but in solution Y I get this problem.

Solution is delete C.dll in project A bin Debug

First make sure all NuGet packages are at the same version across all projects in your solution. E.g., you don’t want one project to reference NLog 4.0.0.0 and another project to reference NLog 4.1.0.0. Then try reinstalling NuGet packages with

Update-Package -reinstall

I had three third-party assemblies that were referenced by my assembly A and only two were included in References by my assembly B which also referenced A.

The missing reference to the third-party assembly was added by the update package command, and the error went away.

I added NuGet package 'StrongNamer' and my problem solved.