How to copy properties from one list to another using Linq conditionally

Question

I have two lists of custom objects.
Both have DivisionId as common propery. I want to copy two parameters, PlanType and CoverageType , from List<Divisions> to List<Members> using Linq, whenever Member.DivisionId = Divisions.DivisionId .

The Member and Divisions objects are given below :

public class Members
{
  public string FirstName;
  public string LastName;
  public string DivisionId;
}

Public Class Divisions
{
  public string PlanType;
  public string CoverageType,
  public string DivisionId;
}

Thanks

Answer 1

What you describe is Join

    var query = from m in members
                join d in divisions on m.DivisionId equals d.DivisionId
                select new { m.FirstName,
                            m.LastName,
                            m.DivisionId,
                            d.CoverageType,
                            d.PlanType
                        };

Answer 2

If you want to copy the item from index 0 in the first list to index 0 in the second, and so on for all of the other indexes you can do this:

var pairs = members.Zip(divisions, (a, b) => new
{
    Member = a,
    Division = b,
});

foreach (var pair in pairs)
{
    Copy(pair.Member, pair.Division);
}

If the indexes don't match you need to do a join:

var pairs = members.Join(divisions
    , member => member.DivisionId
    , division => division.DivisionId
    , (a, b) => new
    {
        Member = a,
        Division = b,
    });

foreach (var pair in pairs)
{
    Copy(pair.Member, pair.Division);
}

Note that the Zip will be faster, if the items are already in the proper order. Join will be slower than the Zip, but will be faster than manually re-ordering the items to allow a Zip .