Few queries about InitializeSimpleMembership class usage in ASP.Net MVC4 - asp.net-mvc-4

Question

i am new in MVC. so i just create a mvc project with vs2013 with internet template. i found one class called InitializeSimpleMembership. tell me what is the usage of this class.
i put break point on this function OnActionExecuting & SimpleMembershipInitializer and saw this function is getting called when i try to access any protected page or when i am clicking on login or register link. i need some insight about this class InitializeSimpleMembership.
what this line is doing LazyInitializer.EnsureInitialized(ref _initializer, ref _isInitialized, ref _initializerLock); ?
tell me what the below routine is doing
public SimpleMembershipInitializer()
{
Database.SetInitializer<UsersContext>(null);
try
{
using (var context = new UsersContext())
{
if (!context.Database.Exists())
{
// Create the SimpleMembership database without Entity Framework migration schema
((IObjectContextAdapter)context).ObjectContext.CreateDatabase();
}
}
WebSecurity.InitializeDatabaseConnection("DefaultConnection", "UserProfile", "UserId", "UserName", autoCreateTables: true);
}
catch (Exception ex)
{
throw new InvalidOperationException("The ASP.NET Simple Membership database could not be initialized.", ex);
}
}
i could understand this line context.Database.Exists() is trying to check a specific db is exist or not. which db it is trying to check exist or not?
what this line is doing WebSecurity.InitializeDatabaseConnection() ?
guide me what i need to do as a result simple membership provider create required table and i could validate user against my database.
tell me what if i need to add more fields then what i need to do.
looking for guidance. thanks

Answer 1

The SimpleMembership provider has been introduced with ASP.NET MVC 4. It extends the core membership and role providers in order to make more flexible the way in which user information are stored in a custom database.
The attribute InitializeSimpleMembershipAttribute takes care of initializing the simple membership provider, defining which context class should be used to work with the database (the UserContext class).
The WebSecurity.InitializeDatabaseConnection initializes the membership system specifying the database through the connection string (“DefaultConnection”), the name of the table in which the user profile data are stored (“UserProfile”) and the name of the field that should be used for the login and so to match the user profile with the membership account.
The method LazyInitializer.EnsureInitialized just ensures that the simple membership is initialized once.
This attribute creates the tables necessary for managing membership in the database specified by the connection string. So it creates the table for the UserProfile model class with the columns “UserId” and “UserName” and uses the “UserId” as a foreign key to relate with the other auto generated tables needed for authentication and authorization.
The AccountController that contains all the basic operations that can be performed on the user profile is decorated with the attribute and in this way every time the user tries to login or register the simple membership is automatically initialized.
http://weblogs.asp.net/jongalloway/simplemembership-membership-providers-universal-providers-and-the-new-asp-net-4-5-web-forms-and-asp-net-mvc-4-templates