My table name is Customer. It has four columns
CustomerId
CustomerName
CustomerAddress
PhoneNo
This is my c# code. I am not ge
As I've said before on this site - the whole User Instance and AttachDbFileName= approach is flawed - at best! Visual Studio will be copying around the .mdf file and most likely, your INSERT works just fine - but you're just looking at the wrong .mdf file in the end!
If you want to stick with this approach, then try putting a breakpoint on the myConnection.Close() call - and then inspect the .mdf file with SQL Server Mgmt Studio Express - I'm almost certain your data is there.
The real solution in my opinion would be to
install SQL Server Express (and you've already done that anyway)
install SQL Server Management Studio Express
create your database in SSMS Express, give it a logical name (e.g. VictoryDatabase)
connect to it using its logical database name (given when you create it on the server) - and don't mess around with physical database files and user instances. In that case, your connection string would be something like:
Data Source=.\\SQLEXPRESS;Database=VictoryDatabase;Integrated Security=True
and everything else is exactly the same as before...