Counting Items in a Collection

[Anonymous]

Hi to all,

Since collections like for example the LayerTable have no Count property (as far as I can see, that is), I'm doing the following to get at the number of items:

Dim LayerCount as integer = 0

For Each Id as ObjectId in SomeLayerTable

    LayerCount +=1

Next

Is this the right way to do it, or is there a more efficient way?

Thanks in advance for your reply.

[Alfred.NESWADBA · Accepted solution]

Hi,

>> Is this the right way to do it

At least it's one of the ways that work.

You should take care of the .IsErased and .IsHidden property as (depending on how you got the layertable) you may count also layers that the user don't see in the layerdialog.

- alfred -

[Anonymous]

 "you may count also layers that the user don't see in the layerdialog"

Hadn't thought about that! Goodyou mentioned that.

Thanks a lot.

[Hallex]

Yo could be use Linq also, but it would be

a bit slower, e.g

        'Imports System.Linq
        <CommandMethod("cnt", CommandFlags.Modal Or CommandFlags.Session)> _
        Public Shared Sub GetLayerCount()
            Dim doc As Document = acApp.DocumentManager.MdiActiveDocument
            Dim db As Database = doc.Database
            Dim ed As Editor = doc.Editor
            Dim LayerCount As Integer = 0
            Using tr As Transaction = db.TransactionManager.StartTransaction

                Dim lt = CType(tr.GetObject(db.LayerTableId, OpenMode.ForRead), LayerTable)
                Dim cnt = (From id As ObjectId In lt
                         Where Not id.IsNull AndAlso Not id.IsErased
                         Select id).Count
                ed.WriteMessage(vbLf + "Layers in the currrent drawing: {0}", cnt)

            End Using
        End Sub

~'J'~

[jeff]

Writing extension methods that return  IEnumrable can be very helpful

A example by Tony T 

http://www.theswamp.org/index.php?topic=41311.msg464457#msg464457

No reason to iterate layertable twice but did for this example

  [CommandMethod("LayerCount")]
        public void LayerCount()
        {
            Document doc = Application.DocumentManager.MdiActiveDocument;
            Database db = doc.Database;
            Editor ed = doc.Editor;


            using (Transaction trx = db.TransactionManager.StartTransaction())
            {

                LayerTable lt = db.GetLayerTable();

                var layers = lt.GetLayerTableRecords()
                    .Where(layer => !layer.IsHidden);

                var erasedLayers = lt.GetLayerTableRecords(OpenMode.ForRead, true)
                    .Where(layer => layer.IsErased);


                ed.WriteMessage("\nLayers " + layers.Count().ToString());
                ed.WriteMessage("\nHidden Layers " + erasedLayers.Count().ToString());

                trx.Commit();
            

            }

        }

[jeff]

Did not think that through as usual but the GetLayerTable extension method probably should have overloads that the parameters indicate to include erased objects, and since a LayerTableRecord can't be on a locked layer it could return all unlocked layers instead to resemble GetObject