Entity Framework returning distinct records after join

Question

Consider we have these two entities and one custom object :

    public class  Entiy1
{
    public int Id { get; set; }
    public int DestinationId { get; set;          


        

Answer 1

Here's a way to do it:

var query = from e1 in
    (from e1 in entities1
        group e1 by e1.DestinationId into grp
        select grp.First())
    join e2 in entities2 on e1.DestinationId equals e2.DestinationId
    select new EntityDTO 
            { 
                DestinationId = e1.DestinationId, 
                DestinationName = e2.DestinationName,
                Name = e1.Name,
                JobTitle = e1.JobTitle
            } ;

The trick is the group by and then taking the first element of the grouping. This is also referred to as "distinct by" that a library like MoreLinq provides out of the box.