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Posts: 95
Registered: ‎01-29-2007
Message 1 of 7 (231 Views)
Accepted Solution

How to determine if entity is a block?

231 Views, 6 Replies
04-15-2014 01:46 PM



I'm writing an app in VB.NET.  In a small part of the code I'm working on, I need to examine each entity in a drawing and determine whether it is a block, and if it is not a block, erase it from the drawing. 


Here's a snip from the part of the code in question.  I can't find an example of how to determine if an entity is a block or not.  Can anyone help me get started filling in the green part below.  Thank you for any suggestions.




Dim myEd As Editor = DocumentManager.MdiActiveDocument.Editor

Dim myPSR As PromptSelectionResult = myEd.SelectAll

 If myPSR.Status = PromptStatus.OK Then

   Dim mySS As SelectionSet= myPSR.Value

   ForEach mySelObj As SelectedObject In mySS

   Dim myEnt As Entity = mySelObj.ObjectId.GetObject(OpenMode.ForWrite)

'If my Entity is not a block or nested within a block, erase it...




Valued Mentor
Posts: 450
Registered: ‎04-11-2010
Message 2 of 7 (208 Views)

Re: How to determine if entity is a block?

04-15-2014 09:05 PM in reply to: edweberg



Instead to test each entity, a better aproach could be to select all entities that do not acomplish the criteria, in this case all entities that are not block references (Block Inserts), this is as easy as using a filter with the "not" operator:


Public Sub DeleteNoBlocksReferences()
        Dim acDoc As Document = Application.DocumentManager.MdiActiveDocument
        Dim acCurDb As Database = acDoc.Database
        Dim ret As SelectionSet

        Using acTrans As Transaction = acCurDb.TransactionManager.StartTransaction()
            Dim acTypValAr(2) As TypedValue

            acTypValAr.SetValue(New TypedValue(DxfCode.Operator, "<not"), 0)
            acTypValAr.SetValue(New TypedValue(DxfCode.Start, "INSERT"), 1)
            acTypValAr.SetValue(New TypedValue(DxfCode.Operator, "not>"), 2)

            Dim acSelFtr As SelectionFilter = New SelectionFilter(acTypValAr)
            Dim acSSPrompt As PromptSelectionResult
            Dim ed As Editor = Application.DocumentManager.MdiActiveDocument.Editor

            acSSPrompt = ed.SelectAll(acSelFtr)

            If acSSPrompt.Status = PromptStatus.OK Then
                ret = acSSPrompt.Value
                Dim objids() As ObjectId
                objids = ret.GetObjectIds
                For Each objid As ObjectId In objids
                    Dim obj As DBObject = acTrans.GetObject(objid, OpenMode.ForWrite)
            End If
        End Using
    End Sub

    <CommandMethod("ENOBLK")> _
    Public Sub enoblk()
    End Sub


Gaston Nunez

Posts: 230
Registered: ‎11-09-2012
Message 3 of 7 (190 Views)

Re: How to determine if entity is a block?

04-16-2014 12:54 AM in reply to: edweberg
you can also try like below:

If Typeof myEnt is BlockReference

'do as you need

Valued Contributor
Posts: 75
Registered: ‎08-10-2007
Message 4 of 7 (172 Views)

Re: How to determine if entity is a block?

04-16-2014 08:30 AM in reply to: edweberg

I support the method of filtering the selection that Gaston has suggested. It's a bit more authoring (and it might take a bit to understand how the .Operators work) but it is an explicit approach that can be easily modified to include specific properties later. Although, it might make more sense when dealing with a large file or when including more function than just erasing the block reference.


If Not TypeOf acObject is BlockReference does what you need though, go for it!

*Expert Elite*
Posts: 5,116
Registered: ‎10-12-2006
Message 5 of 7 (168 Views)

Re: How to determine if entity is a block?

04-16-2014 08:58 AM in reply to: gasty1001

Do selection sets still work when the document isn't active e.g. using a side database?

If you are going to fly by the seat of your pants, expect friction burns.
Adopt. Adapt. Overcome. Or be overcome.
A good question will be halfway to a good answer.

*Expert Elite*
Posts: 2,077
Registered: ‎04-29-2006
Message 6 of 7 (151 Views)

Re: How to determine if entity is a block?

04-16-2014 12:45 PM in reply to: dgorsman



No, you can only use selection sets if the document is opened in the editor (all selection set methods are instance methods of the Editor class).


Using a side database, you'd have to iterate the model (and/or paper) space BlockTableRecord and filter the contained entity.


        private void EraseAllButBlocks(Database db)
            RXClass blockClass = RXClass.GetClass(typeof(BlockReference));
            using (Transaction tr = db.TransactionManager.StartTransaction())
                BlockTableRecord modelSpace = (BlockTableRecord)tr.GetObject(
                    SymbolUtilityServices.GetBlockModelSpaceId(db), OpenMode.ForRead);
                foreach (ObjectId id in modelSpace)
                    if (id.ObjectClass != blockClass)
                        Entity ent = (Entity)tr.GetObject(id, OpenMode.ForWrite);
                        try { ent.Erase(); }
                        catch { }


Gilles Chanteau
Valued Contributor
Posts: 95
Registered: ‎01-29-2007
Message 7 of 7 (142 Views)

Re: How to determine if entity is a block?

04-16-2014 01:14 PM in reply to: _gile

Thank you for all the replies.  I got the solution I needed and much more.



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