topic Re: Block with Multiple Attribute References in .NET Forum

Block with Multiple Attribute References

youssefGC — Mon, 26 Jun 2023 16:53:30 GMT

Hello,

I tried to create a block composed of a polyline and multiple attributes.

Here is the part of the program. Please note that "ScalledPline" is the polyline on which I will create the block, and "_nameofbl" is the name of the block. The variables "insertPoint (point3d), _lstofposition (List<Pointe3d>), _lstoftextstring (List<string>), _lstofrotation (List<double>)" are used to store data related to the attributes (texts, positions, rotations).

// ScalledPline (polyline), insertPoint(point3d), _lstOfPosition (List<Point3d>), _lstOfTextString (List<string>) //_nameOfBl (string), _lstOfRotation (List<double>), insertPoint : given // Get the current database and start a transaction Database db = Application.DocumentManager.MdiActiveDocument.Database; using (Transaction acTrans = db.TransactionManager.StartTransaction()) { // Open the Block table for read BlockTable bt; bt = acTrans.GetObject(db.BlockTableId, OpenMode.ForRead) as BlockTable; ObjectId blkRecId = ObjectId.Null; if (!bt.Has(_nameOfBl)) { using (BlockTableRecord acBlkTblRec = new BlockTableRecord()) { acBlkTblRec.Name = _nameOfBl; // Set the insertion point for the block acBlkTblRec.Origin = insertPoint; // Add pline with attribute onto block using (ScalledPline) { acBlkTblRec.AppendEntity(ScalledPline); // Add an attribute definition to the block for (int i = 0; i < _lstOfDBText.Count; i++) { using (AttributeDefinition acAttDef = new AttributeDefinition()) { acAttDef.Position = _lstOfPosition[i]; acAttDef.Prompt = "Txt N°" + (i + 1).ToString(); acAttDef.Tag = "Txt " + (i + 1).ToString(); acAttDef.TextString = _lstOfTextString[i]; acAttDef.Rotation = _lstOfRotation[i]; acAttDef.Height = 1; acAttDef.Justify = AttachmentPoint.MiddleCenter; acBlkTblRec.AppendEntity(acAttDef); } } bt.UpgradeOpen(); bt.Add(acBlkTblRec); // error in this line acTrans.AddNewlyCreatedDBObject(acBlkTblRec, true); } blkRecId = acBlkTblRec.Id; } } else { blkRecId = bt[_nameOfBl]; } //========== 3 - Insert the block into the current space if (blkRecId != ObjectId.Null) { BlockTableRecord acBlkTblRec; acBlkTblRec = acTrans.GetObject(blkRecId, OpenMode.ForRead) as BlockTableRecord; // Create and insert the new block reference using (BlockReference acBlkRef = new BlockReference(insertPoint, blkRecId)) { BlockTableRecord acCurSpaceBlkTblRec; acCurSpaceBlkTblRec = acTrans.GetObject(db.CurrentSpaceId, OpenMode.ForWrite) as BlockTableRecord; acCurSpaceBlkTblRec.AppendEntity(acBlkRef); acTrans.AddNewlyCreatedDBObject(acBlkRef, true); // Verify block table record has attribute definitions associated with it if (acBlkTblRec.HasAttributeDefinitions) { // Add attributes from the block table record foreach (ObjectId objID in acBlkTblRec) { DBObject dbObj = acTrans.GetObject(objID, OpenMode.ForRead) as DBObject; if (dbObj is AttributeDefinition) { AttributeDefinition acAtt = dbObj as AttributeDefinition; if (!acAtt.Constant) { using (AttributeReference acAttRef = new AttributeReference()) { acAttRef.SetAttributeFromBlock(acAtt, acBlkRef.BlockTransform); acAttRef.Position = acAtt.Position.TransformBy(acBlkRef.BlockTransform); acAttRef.TextString = acAtt.TextString; acBlkRef.AttributeCollection.AppendAttribute(acAttRef); acTrans.AddNewlyCreatedDBObject(acAttRef, true); } } } } } } } // Save the new object to the database acTrans.Commit(); }

Unfortunately, I encountered an issue with a function I'm using : Unhandled Access Violation Reading

Thank you.

Re: Block with Multiple Attribute References

_gile — Tue, 27 Jun 2023 05:12:36 GMT

Hi,

The main issue I see is about ScalledPline.

The polyline should be created within the transaction (acTrans), appended to the block definition and added to the transaction.

To be able to find and correct errors in your code, you should split it into several methods which can be tested separately.

For example:

A 'GetOrCreateBlockDefinition' which checks if the BlockTable contains a bloc definition named as '_nameofbl' and, if it does, return the block definition ObjectId; else, create the block definition, add it to the block table create the polyline and append it to the block definition, create the attributes, add them to the block definition and finally return the ObjectId of this new block definition.

And another 'InsertBlockReference' method, which calls 'GetOrCreateBlockDefinition' to get the ObjectId of the block definition, and inserts a new block reference.

This way, you could first test and debug the 'GetOrCreateBlockDefinition' method until it works before trying to insert the block programmatically.

Re: Block with Multiple Attribute References

shubhamraut221195 — Tue, 27 Jun 2023 06:53:17 GMT

@youssefGC In your code write 'bt.Add(acBlkTblRec)' before 'using (ScalledPline){ }'

Re: Block with Multiple Attribute References

shubhamraut221195 — Tue, 27 Jun 2023 06:54:02 GMT

Right now 'bt.Add(acBlkTblRec)' is inside 'using (ScalledPline){ }'

Re: Block with Multiple Attribute References

shubhamraut221195 — Tue, 27 Jun 2023 07:02:17 GMT

@_gile , When I created new BlockTableRecord and added it to BlockTable & then went for creating polyline , it worked. In code shared by @youssefGC , he is adding BlockTableRecord inside 'using (ScalledPline){ }'. I'm not able to understand how using(){ } works in AutoCAD.NET. I know about 'using(Transaction ....){}' but apart from that I'm not able to understand how 'using(){}' works. Can you please give a hint?

Re: Block with Multiple Attribute References

_gile — Tue, 27 Jun 2023 08:18:23 GMT

@shubhamraut221195 a écrit :

I'm not able to understand how using(){ } works in AutoCAD.NET.

The using statement is not specific to AutoCAD .NET API. It is used to ensure ensures the correct use of an IDisposable instance (see this topic).

using (someDisposableInstance) { // do your stuff with someDisposableInstance }

is equivalent to:

try { // do your stuff with someDisposableInstance } finally { someDisposableInstance.Dispose(); }

Re: Block with Multiple Attribute References

shubhamraut221195 — Tue, 27 Jun 2023 08:31:52 GMT

@_gile Ok. So why can't we add BlockTableRecord to BlockTable inside using(Polyline.....){ }? Is it because polyline which is part of BlockTableRecord which is not disposed yet?

Re: Block with Multiple Attribute References

_gile — Tue, 27 Jun 2023 11:07:03 GMT

@shubhamraut221195 a écrit :

So why can't we add BlockTableRecord to BlockTable inside using(Polyline.....){ }? Is it because polyline which is part of BlockTableRecord which is not disposed yet?

The problem is not adding the BlockTableRecord to the BlockTable inside using(Polyline.....) statement.

The problem is adding a polyline (and AttributeDefinitions) to the BlockTableRecord before having added the BlockTableRecord to the BlockTable.

Typically, the process should be like below (no need to use a using statement for the Polyline because it is always added to the Transaction):

using(Transaction) { Create blockTableRecord Add BlockTableRecord to BlockTable Add BlockTableRecord to Transaction Create polyline Add Polyline to BlockTableRecord Add Polyline to Transaction For each AttributeDefinition Create AttributeDefinition Add AttributeDefinition to BlockTableRecord Add AttributeDefinition to Transaction Commit Transaction }

Re: Block with Multiple Attribute References

youssefGC — Fri, 30 Jun 2023 21:24:27 GMT

Thank you for your reply @_gile,
Yes, indeed, I have examined the code by subdividing it into several methods. In fact,
The problem lies with the "ScalledPline" element, which needs to be added to the "acTrans" transaction before being added as a block.

bt.UpgradeOpen(); bt.Add(ScalledPline); acTrans.AddNewlyCreatedDBObject(ScalledPline, true);

Re: Block with Multiple Attribute References

youssefGC — Fri, 30 Jun 2023 21:29:08 GMT

Yes, but the source of the problem is that I am adding "ScalledPline" to a block before it is added to the transaction.

Re: Block with Multiple Attribute References

_gile — Sat, 01 Jul 2023 04:58:10 GMT

@youssefGC a écrit :

Thank you for your reply @_gile,
Yes, indeed, I have examined the code by subdividing it into several methods. In fact,
The problem lies with the "ScalledPline" element, which needs to be added to the "acTrans" transaction before being added as a block.
bt.UpgradeOpen(); bt.Add(ScalledPline); acTrans.AddNewlyCreatedDBObject(ScalledPline, true);

In this snippet, you add the polyline to the block table which does not make sense (you can only add new BlockTableRecord instances to the block table).

We do not know where the ScalledPline comes from, how it have been created.

Typically, it should be created inside the same transaction the new block definition (BlockTableRecord) is created and appended to this block definition and the transaction as described in the pseudo code of this reply.

Re: Block with Multiple Attribute References

youssefGC — Sat, 01 Jul 2023 09:26:41 GMT

Sorry, I didn't explain the origin of "scalledPline" properly. In fact, in my main program, "scalledPline" is a polyline resulting from a Jig. Then, I want to create a block using this polyline.

Finally, I want to save the original polyline, as well as create a block (based on the polyline, of course), and insert it in another location.

Re: Block with Multiple Attribute References

_gile — Sat, 01 Jul 2023 15:13:26 GMT

@youssefGC a écrit :

Sorry, I didn't explain the origin of "scalledPline" properly. In fact, in my main program, "scalledPline" is a polyline resulting from a Jig. Then, I want to create a block using this polyline.

Finally, I want to save the original polyline, as well as create a block (based on the polyline, of course), and insert it in another location.

The same polyline cannot be added to several BlockTableRecords (the model space and a block definition).

You could add the polyline to the model space after the Jig and pass its ObjectId to the method where you create the block definition. In this method, you can use DeepCloneObjects to copy the polyline into the newly created block definition.

Pseudo code:

using(Transaction) { Create blockTableRecord Add BlockTableRecord to BlockTable Add BlockTableRecord to Transaction DeepClone the polyline For each AttributeDefinition Create AttributeDefinition Add AttributeDefinition to BlockTableRecord Add AttributeDefinition to Transaction Commit Transaction }