Question

I need to select distinct highways from a roads collection.

I suppose I could use LINQ for this.

I have (stub code)

  Dim roads As List(Of Roads) = myRegion.Roads
  Dim highways As New List(Of Highway)

  For Each road In roads
    If road.RoadType = RoadType.Highway Then
      highways.Add(DirectCast(road, Highway))
    End If
  Next ic

  ' Now I think sorting them by .Id and then remove duplicates '
  Dim myComparer As New HighwayByIdComparer
  highways.Sort(myComparer)

C# variants are accepted as well 😉

Answer 1

C#:

return myRegion.Roads
    .Where(x => x.RoadType == RoadType.Highway)
    .DistinctBy(x => x.Id);

(where DistinctBy is an extension method defined in Jon Skeet’s excellent MoreLINQ project)