There are diff ways to allow the user to login. Windows Authentication, Forms Authentication.

I want to ask that in depends on which situation,dat which method to use??

When I create a login form. I always login using
Code:
 SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString);
WEB.CONFIG
Code:
<configuration>
	<appSettings/>
  <connectionStrings>
    <add name="ConnectionString" connectionString="Data Source=(local);Initial catalog=sonia;User ID=sonia;Password=sonia;" providerName="System.Data.SqlClient"/>
  </connectionStrings>
  <system.web>
Above is which type of method???