Problems with casting LinQ result to strongly typed collection.

Question

Hi guys. I guess this is trivial but not for me.

I have a collection MembershipUserCollection. I wanted to perform some Linq query over it so I've used OfType<MembershipUser>() method and then applied Where() on it. However, I do not know how to cast back my results to MembershipUserCollection?

This is my code:

MembershipUserCollection Users;
Users = GetAllUsers(pageIndex, pageSize, out totalRecords).OfType<MembershipUser>().Where(user => user.Email == emailToMatch); //how to cast it back to MembershipUserCollection ?

GetAllUsers(pageIndex, pageSize, out totalRecords) is returning MembershipUserCollection

Thanks for your time.

Answer 1

I don't think you can do it in the query itself, but you should be able to do this:

var query = GetAllUsers(pageIndex, pageSize, out totalRecords)
                .OfType<MembershipUser>()
                .Where(user => user.Email == emailToMatch);

var users = new MembershipUserCollection();
foreach (var user in query)
{
    users.Add(user);
}

(And, of course, you could wrap that logic up into an extension method if you wanted and then call the extension method in the query.)

Answer 2

One of the possible solutions:

   var users = GetAllUsers(pageIndex, pageSize, out totalRecords)
      .OfType<MembershipUser>()
      .Where(user => user.Email == emailToMatch);

   MembershipUserCollection membershipUsers = new MembershipUserCollection();
   users
      .ToList()
      .ForEach(membershipUsers.Add);

Another one with foreach statement:

foreach (var user in users)
{
    membershipUsers.Add(user);
}

Answer 3

So it was trivial, I just had to cast it like this:

MembershipUserCollection Users;
Users = (MembershipUserCollection)GetAllUsers(pageIndex, pageSize, out totalRecords).OfType<MembershipUser>().Where(user => user.Email == emailToMatch).Cast<MembershipUser>();

Thanks guys for your asnwers.