MVC3 changing default connection string error - sql-server

Question

I created an MVC3 Internet application and changed the default connection string to work with
.\SQLSERVER instead of the default .\SQLEXPRESS and get following error :
A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Shared Memory Provider, error: 40 - Could not open a connection to SQL Server)
I tried creating an empty MVC3 application as well, which has no connection string by default and added mine with the same result.
The SQLSERVER instance is running and I can connect to it from management studio using windows authentication. Any connection string that I use gives same error, I cannot figure it out:
<connectionStrings>
<remove name="LocalSqlServer" />
<add name="LocalSqlServer" connectionString="data source=.\SQLSERVER;" providerName="System.Data.SqlClient" />
</connectionStrings>

Answer 1

To connect to your local default instance (i.e. SQLSERVER service name), for Data Source=..., use one of the following:
127.0.0.1
localhost
(local)
.
EDIT
Your connection string should resemble this:
Data Source=myServerAddress;Initial Catalog=myDataBase;User Id=myUsername;Password=myPassword;

Answer 2

Checkout the different connection strings you can use with SQL Server. For example if you have a SQL Server installed on your local machine you could use the following connection string:
Data Source=127.0.0.1;Initial Catalog=myDataBase;User Id=myUsername;Password=myPassword;
Obviously you will need to adjust the name of the database, the username and password to connect to.
If you want to use Windows Authentication to connect to the server:
Data Source=127.0.0.1;Initial Catalog=myDataBase;Integrated Security=SSPI;

Answer 3

Your connection string needs to look something like this:
<add name="NameOfConnection" connectionString="Data Source=localhost;Initial Catalog=OMSCING;Trusted_Connection=Yes" providerName="System.Data.SqlClient" />
Where you can replace localhost with a hostname or leave it like that if the server's local.

Answer 4

Perhaps I had to mention that I was using EF with code first approach, but the problems was due to the name of the connection string which should be the same name as your Context which you derive from DbContext, e.g.:
<connectionStrings>
<remove name="ApplicationServices"/>
<add name="MyContext"
connectionString="data source=localhost; Initial Catalog=CoolCars;Integrated Security=True;" providerName="System.Data.SqlClient" />
</connectionStrings>
as well make sure you remove the default machine.config connection string which is for .\SQLEXPRESS