I receive many e-mails asking how to use embedded Firebird with ASP.NET applications. This looks very appealing, especially for the hosted websites - imagine just copying your database engine together with your application to the server.... But unfortunately, it is not so easy:

Problem #1 - How to find fbembed.dll

The fbembed.dll is not a managed assembly, it's a classical DLL called using PInvoke (DllImport attribute). By default, the Firebird ADO.NET Provider is looking for the fbembed.dll in the default paths, which includes the system directory (e.g. C:\Windows\System32) but not the ASP.NET application bin directory. This is a problem when you don't have the access to the system directory - this is something that your hosting provider rarely allows you to.

The solution is to use the "clientlibrary" parameter in connection string and specify path to fbembed.dll.

Problem #2 - Overlapped Worker Process Recycling on IIS6

ASP.NET uses a feature that help against poorly written ASP.NET application to block the entire server - it recycles the ASP.NET working process both regularly. By default, IIS6 uses overlapped recycling where there is a new process started before the old is stopped to ensure uninterrupted operation. The problem is that the fbembed.dll exclusively locks the database for the owner process so if you run another process simultaneously the database won't be accessible before the first process stops. You might want to accept this but it really is not an optimal solution.

The solution is to turn off the overlapped recycle (by setting the DisallowOverlappingRotation metabase property to true). However, this might cause outages of your application during recycle.

Conclusion

Don't do that ;-). Really, fbembed.dll was not built to handle such use. You can make it work but it is just a hack.