The TCP/IP connection to the host localhost, port 1433 has failed. Error: "Connection refused: connect. Verify the connection properties, check that an instance of SQL Server is running on the host and accepting TCP/IP connections at the port, and that no firewall is blocking TCP connections to the port.
Verifique que la configuración de su servidor SQL permita aceptar conexiones TCP/IP. Habilite TCP/IP y reinicie SQL Server. Luego prueba tu código nuevamente.
