如何使用LINQ避免冗余List

Question

I have a Report object that has Recipients property (of String datatype). The Recipients property will hold all the recipients' email address in comma separated string . I need to create a “ Collection ” of Email objects from the comma separated string. I have the following code that uses a List of string to get the email address first. Then I create a collection of email objects.

Is there a better way to avoid the redundant List and Collection using LINQ ?

  Report report = new Report();
  report.Recipients   = "test@test.com, demo@demo.com";

  List<string> emailAddressList = new List<string>( report.Recipients.Split(',') );
  Collection<Email> emailObjectCollection = new Collection<Email>();

  foreach (string emailAddress in emailAddressList)
  {
           Email email = new Email();
           email.EmailAddress = emailAddress;
           emailObjectCollection.Add(email);
  }

References :

1. Better code for avoiding one dictionary - Case Sensitivity Issue
2. Remove duplicates in the list using linq
3. Using LINQ to find duplicates across multiple properties
4. C#: Difference between List<T> and Collection<T> (CA1002, Do not expose generic lists)

CA1002 : Do not expose generic lists. System.Collections.Generic.List is a generic collection designed for performance not inheritance and, therefore, does not contain any virtual members. http://msdn.microsoft.com/en-us/library/ms182142(v=vs.80).aspx

Answer 1

You can just use a HashSet .

var emailObjectCollection = new HashSet<Email>(
     report.Recipients.Split(',').Select(e => new Email() { EmailAddress = e }));

Answer 2

var  emailObjectCollection =   report.Recipients.Split(',')
                                    .Select(m=>new Email(){EmailAddress = m})
                                    .ToList()

Answer 3

Just off the top of my head:

var emailObjectCollection = new Collection<Email>(
    new List<string>(report.Recipients.Split(',')).Distinct()
        .Select<string, Email>(e => 
        {
            var email = new Email();
            email.EmailAddress = e;
        }).ToList());

That should be the LINQ-y way of populating a Collection<T> with unique values. Just curious though, why use a Collection ? If you need to pass this enumerable around, would it not make more sense to use IEnumerable ?

Plus, you could suppress the CA1002 message with a suppression attribute - there are valid exceptions to the rule, from time to time (IMHO).