Quote:
once I deploy it to another computer that DO NOT have sql server express.
If there's no SQL server instance installed, you can't run your programme, no matter what you write in the connection string.
You've got two options to resolve your issue:
1) create one SQL server in a LAN/WAN and enable remote connections to it -
strongly recommended!
or
2) install SQL server instance on each computer you want deploy your programme -
not recommended at all! due to several reasons, but the most important is: you'll be in trouble with data synchronization.
So, follow this link:
Configure the remote access Server Configuration Option - SQL Server | Microsoft Docs[
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