PS0240: Strong Name API Failed

Cause

When the project has a strong name, PostSharp signs the assembly that it produces with the same key as the C# compiler. On Windows, PostSharp uses the strong name API of the .NET Framework (IClrStrongName, in mscoree.dll) to read the key and to sign the file whenever the PostSharp compiler runs on the .NET Framework, and, on .NET, when the key is in a key container (the KeyContainerName MSBuild property) rather than in a key file.

PostSharp reports PS0240 when this API fails, either while it reads the information of the key or while it signs the file. It is a fatal error: PostSharp stops at once. <Details> names the key file or the key container, or the file being signed, and gives the error of the API. When the error is 0x8013141C, the message adds that access to the C:\ProgramData\Microsoft\Crypto\RSA\MachineKeys folder may be blocked, for example by an antivirus. PostSharp retries several times before it reports this error, and also retries when another process locks the file.

This message depends on the cryptographic configuration of the machine, so no example can show it.

Resolution

• When the project uses a key container, check that the container exists on the machine that runs the build, under the account that runs it, for example with sn -pc <container> public.snk. A key container is local to a machine: on a build server, install it there, or use a key file instead.
• Prefer a key file: set the AssemblyOriginatorKeyFile MSBuild property to the path of the .snk file, with SignAssembly set to True, and remove KeyContainerName. With a key file, PostSharp does not call the strong name API on .NET.
• When the error is 0x8013141C, check that the account that runs the build can read and write C:\ProgramData\Microsoft\Crypto\RSA\MachineKeys, and exclude this folder and the obj folder of the project from the scans of your antivirus.
• To see each call that PostSharp makes to the strong name API and the exceptions it gets, build with the PostSharpTrace MSBuild property set to StrongName and a build log verbosity of at least normal. See Well-Known MSBuild Properties.

See Also

Other Resources

Well-Known MSBuild Properties