what will be username and password in connection string for sql server authentication when using window authentication

We Do not need to Add username and Password

just write in web.config-

<connectionstrings>
		<add name="Connect" connectionstring="Data Source=.\sqlexpress;database=Musicmania;integrated security=true;MultipleActiveResultSets=True" providername="System.Data.SqlClient" />
	</connectionstrings>

or in CS-

SqlConnection sqlconn = new SqlConnection("server=.\\sqlexpress;database=db;integrated security=true");

In Case if you're Using Sql server Authentication then-

SqlConnection sqlconn = new SqlConnection("server=.\\sqlexpress;database=db;user id=ur userid;password=ur password;");

hi ,

please follow this steps
step1.
open page like test.aspx ,

step2.
on a Design of a page drag and drop any table from database , it will display like gridview dont worry.

step3.

go to web.config file you can see your connection string.