Fail to connect to SQL Server database - asp.net

Question

I am using VS 2008 .NET 3.5 & have a SQL Server database file in App_Data. When I click on "Test Connection" of database it succeeds. When I try to connect it through code, it fails. After trying to find & solve the problem reading so many sites, I think I am confused with the connection string.
My code is :
string sql = "select count(*) from LoginDB where loginUserName = #userName and loginPassword = #password";
string conStr = ConfigurationManager.ConnectionStrings["VinciConnectionString"].ConnectionString;
statusLbl.Text += "\n Conn Str = " + conStr;
conn = new SqlConnection(conStr);
statusLbl.Text += "\n Executed Conn : " + conn.ToString();
SqlCommand cmd = new SqlCommand(sql, conn);
statusLbl.Text += "\nconn DB = " + conn.Database;
In the output I get :
Conn Str = server=localhost;database=VincitoreDB.mdf;uid=VTSONY\Vikram10;Password=000;
Executed Conn : System.Data.SqlClient.SqlConnection
conn DB = VincitoreDB.mdf
SQL = System.Data.SqlClient.SqlCommand
The error message that I get here is :
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: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)
The DB "Modify Properties"-"Advanced" tab shows this :
Original connection string was :
<connectionStrings>
<add name="VinciConnectionString"
connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\VincitoreDB.mdf;Integrated Security=True;User Instance=True"
providerName="System.Data.SqlClient" />
</connectionStrings>
After trial & error, right now it's :
<connectionStrings>
<add name="VinciConnectionString"
connectionString="server=localhost;database=VincitoreDB.mdf;uid=VTSONY\Vikram10;Password=000;"
providerName="System.Data.SqlClient" />
</connectionStrings>
Can anyone please help me figure out what & why am not able to connect to the database? Have spend lots of hrs trying to figure out reading lots of forums, but no success. If this the problem of connection string or something else?
Please help me out. Any help is highly appreciated.
Thanks

Answer 1

Enable in your Sql Server Configuration manager under SQL Server Networki configuration > Protocols fro SQLExpress > TCP IP - Enabled after this restart the computer or the service.
In connection string provide your computers name for example: MY-PC\SQLEXPRESS