I have some code that broke after updating to 7.1.1 from 6.5. I have a program, a custom installer application we wrote, that is only ever run on the same computer where Firebird is installed. Previously because the application already had verified that it was being run on the server, I didn't bother to specify that the DataSource property on FbConnectionStringBuilder should be set to localhost. After updating to 7.1.1, this lack of providing the DataSource explicitly broke our application. I am sorry, but I have not reverted back to 6.5 to prove whether the FbConnectionStringBuilder is the one forgetting to specify that the DataSource should be localhost by default or whether it is instead the FbConnection class that can no longer handle not being provided a DataSource.
An invalid connection string argument has been supplied or a required connection string argument has not been supplied.
It is my opinion that this probably should be something where you probably want to keep applications that did not provide the DataSource from breaking when they update to the latest ADO.NET driver. I know that in most scenarios you will want to provide a DataSource, but localhost seems to have been the default up until now and that is probably a pretty safe bet if one was not provided.