I think that the picture below is self explanatory. The problem is that I start adding a ADO.NET Entity data model with database first but whenever I try to do it, I don't get a connection string when I choose the type of connection. Hope the picture will be of help because I don't know exactly how to describe the problem.
you should, open the SQL Server Configuration Manager and
1) verify the sql server service is up
2) make sure the server and client protocols are set
3) verify your sql server instance NAME. for ex) . or .\SQLEXPRESS or something else
4) check your firewall
best of luck.
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