Connecting to SQL express

i build application for my work, and the only problem that im having is that i cant connecto to the server on my desktop computer. i put this connection string in my app and from my pc to my pc i connect.

"Data Source=sony-02391;Initial Catalog=QADB.MDF;Integrated Security=SSPI;"

the issue is when i copy the app to another pc on the network it says that cannot connect. is there any problem if the other pc is outside the workgroup im in.?

thank you in advance for your help guys. im new in programming. thanks again.

The Data Source should be SERVER_NAME\INSTANCE_NAME. See www.connectionstrings.com for the appropriate format for all sorts of connections.

"Data Source=sony-02391.\SQLExpress;Initial Catalog=QADB.MDF;Integrated Security=SSPI;"

??? like that - im sorry im new to SQL

Does your server name have a dot in it? In a path a dot stands for the current, so ".\SQLEXPRESS" means the SQL Server instance named SQLEXPRESS on the current machine. If SQLEXPRESS is not the name of your instance then change it. If the instance is not on the current machine then supply the name of the machine that it's on. I thought that SERVER_NAME\INSTANCE_NAME was pretty clear.