How to sort all users by username which get from Membership.GetAllUsers() ?

I use Membership.GetAllUsers() to get all users and pass them to MembershipUserCollection, I hope these the users can be sort by UserName,
so I use LINQ to do it, but I get error.  how can I do?


MembershipUserCollection myAllUser = Membership.GetAllUsers();

var result = from user in myAllUser
             orderby user.UserName
             select user;

var result = from user in myAllUser.GetEnumerator()
             orderby user.UserName
             select user;

...