EF Code First DBContext and Transactions

I would like know what is the best possible way to implement transactions with DBContext. In particular,

1. Does DbContext.SaveChanges implement transaction internall if i change multiple entities?
2. If i want to call DbContext.SaveChanges multiple times(same contxet/different contxets), how transaction can be achieved?

1. Yes. SaveChanges uses transaction internally.
2. Use TransactionScope to wrap multiple calls to SaveChanges

Example:

using(var scope = new TransactionScope(TransactionScopeOption.Required,
    new TransactionOptions { IsolationLevel = IsolationLevel.ReadCommitted }))
{
    // Do something 
    context.SaveChanges();
    // Do something else
    context.SaveChanges();

    scope.Complete();
}