Wednesday, September 14, 2011

Assembly must be Strong Signed in order to be marked as a Prerequisite

In the process of trying to update and rebuild a C# project utilizing Microsoft's Enterprise Library, I inexplicably got the error "Microsoft.Practices.EnterpriseLibrary.Data.dll must be strong signed in order to be marked as a prerequisite." 

I hadn't touched this project in a while, in fact I may've last built it on a different PC, so I guess if I had strong signed the Enterprise Library dll, the new system had no idea. Also, I'd installed .NET 4 recently, so maybe this had something to do with this earlier version of the Enterprise LIbrary (my project implements 4.1 whereas the latest version is 5). I guess security in the .NET 3.5 framework isn't up to snuff as far as .NET 4 is concerned.

Anyway, it appeared I had no choice but to use the sn.exe utility and create a key pair and do all the stuff Microsoft suggests in their painfully tedious article on how to sign an assembly with a strong name. Luckily after some digging I found Signer, a command-line utility which simplifies the process of strongly signing one or more assemblies which VS 2008 may be complaining about.

I'm referencing this from the perspective of a Windows 7 64-bit system, so note that the following may vary if you're using 32-bit. 

In order to do it's thing, Signer requires access to some other command line utilities, most of which live in C:\Program Files\Microsoft SDKs\Windows\v6.0A\Bin\. A few, however, including ilasm.exe and fusion.dll, live elsewhere (in my case, these were hanging out in C:\Windows\Microsoft.NET\Framework64\v4.0.30319).

I decided to copy Signer.EXE to the above SDK path, and copy the latest versions of the above files to that same path, so that when I execute Signer.EXE, it'll be able to easily find all the external EXE and DLL files in the same directory.

First of all, though, I needed to use MIcrosoft's sn utility to create an .snk key file in my SDK folder from a command prompt as follows:
sn.exe -k 1024 myProjectKeyName.snk

This instructs sn to produce a key file named myProjectKeyName.snk which I really don't care about for anything other than getting my project to build again. Thus, I chose an arbitrary key file name and value of 1024-bit key length.

I then executed Signer as follows in the same folder:
signer.exe -k myProjectKeyName.snk -outdir C:\myProject\myProjectLibrary -a C:\myProject\myProjectLibrary\*.dll

Here I'm instructing Signer to take the key I just created and strongly sign all .DLL files in my project's library folder. After this, I did a Clean Build on my project, then a Build, and thank goodness, the build completed successfully!
Even though Visual Studio 2008 can't build .NET 4 applications, I guess nevertheless since I have the .NET 4 framework installed, it's mandated that all assemblies shall be strong signed, or the project using them shall not build. Whatever, I'm just happy to have gotten past this issue.

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