Question

I’m writing a piece of code with linq which has to hash a string (in that case my login) and then try to find it into my database.

I tried :

var userFind = context.Users.FirstOrDefault(user =>HashHelper.HashCode(user.Login).Equals(u.Login));

I got an error because of the HashCode.
I wouldn’t read all of my list with a foreach. I’m wondering if it’s possible to do so with one line of code.
Regards.

Edit: I found a way to do so, but it isn’t as lighter as I expected.

  User userFind = null;
            foreach (var user in context.Users)
            {
                string hashedLogin = HashHelper.HashCode(user.Login);
                if(hashedLogin.Equals(u.Login))
                {
                    userFind = user;
                }
            }

Answer 1

If you don’t have too many users, you can do it on one line like this.

var userFind = context.Users.ToList().FirstOrDefault(
    user => HashHelper.HashCode(user.Login).Equals(u.Login))

The important bit is the ToList() which evaluates the EF part and makes the rest linq-to-objects. This means the comparison will be done on the client and all users will be retrieved from the server. It is equivalent to your edit.

If performance is a problem you should store the hashcode in the database too.