.net – How to strong name an assembly that is shared by several developers

.net-assemblycomdelay-signnetstrongname

My colleagues and I have a C# project must be registered with COM using either regasm.exe or RegistrationServices for Excel interop. As a result, the assembly must be signed with a strong name key. A key file was generated through Visual Studio and committed to the source code repository.

Every time a new developer clones the git repository they must either go to the signing tab of the project properties and re-enter the password for the .pfx file or re-enter the password using sn.exe on the command line. Neither is ideal because both require manual steps and verbal communication of the (easy, widely known) password.

We tried delay signing the assembly which allowed the build to proceed but didn't let us register with COM.

Is there a way to do this without forcing everyone to manually update .pfx key files? Thanks!

Best Answer

[ComVisible] assemblies do not require a strong name. The default action for regasm.exe is to assume you'll deploy the assembly into the GAC. That is however not a requirement, give it the /codebase option to register it in the directory where it is located. Typically the build directory of the project.

This is also what Visual Studio does when you tick the "Register for COM interop" option in the Build properties. Now simply building the project is enough. Do check if this is still compatible with your installer. There are DLL Hell implications, best solved with isolation btw.

Related Solutions

C# – How to enable assembly bind failure logging (Fusion) in .NET

Add the following values to

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Fusion
Add:
DWORD ForceLog set value to 1
DWORD LogFailures set value to 1
DWORD LogResourceBinds set value to 1
DWORD EnableLog set value to 1
String LogPath set value to folder for logs (e.g. C:\FusionLog\)

Make sure you include the backslash after the folder name and that the Folder exists.

You need to restart the program that you're running to force it to read those registry settings.

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C# – 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

Disassemble the assembly using ildasm.exe and save the intermediate language (IL):
```
ildasm /all /out=thirdPartyLib.il thirdPartyLib.dll 
```

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
}