sql connection string in asp.net

Connetion string used for mssql server which is installed in you server.

SqlConnection sqlcon = new SqlConnection("data source=localhost;Initial Catalog= ur database name; User Id=XXX; Password=XXX");

Connetion string used for mssql server which is installed in you system(ie .sql
server management studio express)

SqlConnection sqlcon = new SqlConnection("Server=.\\SQLExpress;Initial Catalog=ur database name; User Id=XXX; Password=XXX; Integrated security=true");