Find list of blocks in drawing but no instance visable

[conveyor1]

I am looking for a VB.net way to search for a blocks name in a drawing where the block current has no visable instance. For example, if I have a block named "temp" that has previously been inserted into the drawing, but has been deleted, but not purged, how can I find this block by its name or other means?

Please let me know your thoughts.

[_gile]

Hi,

You can use the Database.Purge() method to ge unreferenced blocks.

        public List<string> GetUnreferencedBlockNames(Database db)
        {
            var result = new List<string>();
            using (var tr = db.TransactionManager.StartOpenCloseTransaction())
            {
                ObjectIdCollection blockIds = new ObjectIdCollection();
                var bt = (BlockTable)tr.GetObject(db.BlockTableId, OpenMode.ForRead);
                foreach (ObjectId id in bt)
                {
                    blockIds.Add(id);
                }
                db.Purge(blockIds);
                foreach (ObjectId id in blockIds)
                {
                    var block = (BlockReference)tr.GetObject(id, OpenMode.ForRead);
                    result.Add(block.Name);
                }
            }
            return result;
        }

[_gile]

Another way using the BlockTableRecord.GetBlockReferenceIds() method.

This one does not care if the block definition is hard referenced by some other object than a block reference.

        public List<string> GetUnreferencedblockNames(Database db)
        {
            var result = new List<string>();
            using (var tr = db.TransactionManager.StartOpenCloseTransaction())
            {
                var bt = (BlockTable)tr.GetObject(db.BlockTableId, OpenMode.ForRead);
                foreach (ObjectId id in bt)
                {
                    var btr = (BlockTableRecord)tr.GetObject(id, OpenMode.ForRead);
                    if (!btr.IsLayout && btr.GetBlockReferenceIds(true, true).Count == 0)
                    {
                        result.Add(btr.Name);
                    }
                }
            }
            return result;
        }

[ActivistInvestor · Accepted solution]

You can use the BlockTable's indexer to find the ObjectId of a BlockTableRecord given the block's name.

You can use the BlockTable's Has() method to find out if a block with the given name is defined in a drawing.

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@conveyor1wrote:
I am looking for a VB.net way to search for a blocks name in a drawing where the block current has no visable instance. For example, if I have a block named "temp" that has previously been inserted into the drawing, but has been deleted, but not purged, how can I find this block by its name or other means?

Please let me know your thoughts.

---

[conveyor1 · Accepted solution]

Here is what I used to get the required result. (TextBoxForm32 has the name of the Block).

' Check if Block Exists
Dim mydwg As Document = Application.DocumentManager.MdiActiveDocument
Dim mytransMan As Database = mydwg.Database
' Get the current document and database, and start a transaction
Using mytrans As Transaction = mytransMan.TransactionManager.StartTransaction()
' Open the Block table record for read
Dim mybt As BlockTable
mybt = mytrans.GetObject(mytransMan.BlockTableId, OpenMode.ForRead)
If (mybt.Has(TextBoxForm32)) Then
Else
Form_Error = True
MsgBox("Load the Drawing Template for dot Net")
End If
' Dispose of the transaction
mytrans.Dispose()
End Using