I can't seem to figure out how to set the default database in Sql Server from code. This can be either .Net code or T-Sql (T-Sql would be nice since it would be easy to use in any language). I searched Google and could only find how to do it in Sql Server Management Studio.
ALTER LOGIN
should be used for SQL Server 2005 or later:
http://technet.microsoft.com/en-us/library/ms189828.aspx
ALTER LOGIN <login_name> WITH DEFAULT_DATABASE = <default_database>
sp_defaultdb
eventually will be removed from SQL Server: