Vad ca in connection string nu este prezent numele bazei de date...

In BOL ---> Sql Server Programming reference ---> Building applications with SQL Native Client ---> Using Connection String Keywords with SQL Native Client se specifica:

 "AttachDbFileName:

The name of the primary file (include the full path name) of an attachable database. To use AttachDBFileName, you must also specify the database name with the provider string Database keyword. If the database was previously attached, SQL Server does not reattach it (it uses the attached database as the default for the connection)."