Datasource is the address of our database server..
for using local database you can write a local or put only .(dot) insted of writing some thing...
look at my connection string for demonstartion
"Data Source=.;Initial Catalog=MyEcommerce;Integrated Security=True"
or
"Data Source=(local)\SQLEXPRESS;Initial Catalog=MyEcommerce;Integrated Security=True"
or
"Data Source=Tejas-Laptop\SQLEXPRESS;Initial Catalog=MyEcommerce;Integrated Security=True"