C# LINQ Solution

Question

I'm writing am application that I've previously posted questions on here, but I'l looking for some more similar advice of possible. I am looking for how best to write my code, as I have a working example, but to me feels long winded. I'm new to LINQ.

The Application first grabs 3 tables via DataContext:-

        var contacts = db.GetTable<Contact>();
        var distributionLists = db.GetTable<DistributionList>();
        var JunctionTable = db.GetTable<ContactsDistribution>();

I then get the selected items from my listbox, these are distribution lists. A contact can be in more than one distribution list, so i first get the raw data from my database:-

var listBoxItems = listBox1.SelectedItems.Cast<object>().Select(t => t.ToString());

var initialList = (from j in JunctionTable
                      where listBoxItems.Contains(j.DistributionName)
                      join c in contacts on j.ContactID equals c.ContactID
                      select new { c.ContactID,c.Surname,j.DistributionName, j.EmailFlag, j.SMSFlag}).ToList();

I then need to search the initialList collection for users who require Email Notifications, I also need to remove duplicate entries, as a Contact can appear multiple times. So the list is made Distinct:-

var email = (from l in initialList
                       where l.EmailFlag.Equals(true)
                       select new { l.ContactID }).Distinct().ToList();

I then do the same search for Contacts that require SMS Notification from the selected lists :-

var sms = (from l in initialList
                       where l.SMSFlag.Equals(true)
                       select new { l.ContactID }).Distinct().ToList();

Now that i have lists for both SMS & Email Notifications I need get the required Email Address or mobile number by doing this :-

var smsMobileNumbers = (from s in sms
                        join c in contacts on s.ContactID equals c.ContactID
                        select new { c.MobileNumber }).ToList();

var emailAddresses = (from m in email
                     join c in contacts on m.ContactID equals c.ContactID
                     elect new { c.EmailAddress }).ToList();

My Question would be, Is there a cleaner way of writing this code or a better, more efficient way of achieving this.

Answer 1

The only change I would make would be to remove the two statements where you create the lists sms and email. They are redundant: by adding the EmailAddress and MobileNumber to the query where you are creating the initialList, you can do a select on the initialList.

var initialList = (from j in JunctionTable
                where listBoxItems.Contains(j.DistributionName)
                join c in contacts on j.ContactID equals c.ContactID
                select new { c.ContactID, c.Surname, c.EmailAddress, c.MobileNumber, 
                                j.DistributionName, j.EmailFlag, j.SMSFlag }).ToList();

I changed these more because I like this syntax better than the SQL like Linq.

var emailAddresses = initialList
    .Where(l => l.EmailFlag)
    .Select(l => l.EmailAddress).Distinct().ToList();

var smsMobileNumbers = initialList
    .Where(l => l.SMSFlag)
    .Select(l => l.MobileNumber).Distinct().ToList();