You can extract attribute information from a block reference using the AttributeCollection property. The AttributeCollection property returns a collection of the attribute references attached to a block. When stepping through the collection, you can use the IsConstant property to see if an attributes value can be changed or not.
You do not need template files to extract attribute information, and no attribute information files are created. Simply iterate the collection of attribute references, using the Tag and TextString properties of the attribute reference to examine the attribute information. You will also need to check to see if IsMTextAttribute is True or False, if True you will need to get the text value for the multiline attribute with the MTextAttribute property.
For more information on extracting attribute information, see “About Extracting Data from Block Attributes” in the product Help system.
This example creates a block and then adds an attribute to the block. The block is then inserted into the drawing. The attribute data is then returned and displayed using a message box. The attribute data is then updated for the block reference, and once again the attribute data is returned and displayed.
Imports Autodesk.AutoCAD.Runtime
Imports Autodesk.AutoCAD.ApplicationServices
Imports Autodesk.AutoCAD.DatabaseServices
Imports Autodesk.AutoCAD.Geometry
<CommandMethod("GettingAttributes")> _
Public Sub GettingAttributes()
' Get the current database and start a transaction
Dim acCurDb As Autodesk.AutoCAD.DatabaseServices.Database
acCurDb = Application.DocumentManager.MdiActiveDocument.Database
Using acTrans As Transaction = acCurDb.TransactionManager.StartTransaction()
' Open the Block table for read
Dim acBlkTbl As BlockTable
acBlkTbl = acTrans.GetObject(acCurDb.BlockTableId, OpenMode.ForRead)
Dim blkRecId As ObjectId = ObjectId.Null
If Not acBlkTbl.Has("TESTBLOCK") Then
Using acBlkTblRec As New BlockTableRecord
acBlkTblRec.Name = "TESTBLOCK"
' Set the insertion point for the block
acBlkTblRec.Origin = New Point3d(0, 0, 0)
' Add an attribute definition to the block
Using acAttDef As New AttributeDefinition
acAttDef.Position = New Point3d(5, 5, 0)
acAttDef.Prompt = "Attribute Prompt"
acAttDef.Tag = "AttributeTag"
acAttDef.TextString = "Attribute Value"
acAttDef.Height = 1
acAttDef.Justify = AttachmentPoint.MiddleCenter
acBlkTblRec.AppendEntity(acAttDef)
acBlkTbl.UpgradeOpen()
acBlkTbl.Add(acBlkTblRec)
acTrans.AddNewlyCreatedDBObject(acBlkTblRec, True)
End Using
blkRecId = acBlkTblRec.Id
End Using
Else
blkRecId = acBlkTbl("TESTBLOCK")
End If
' Create and insert the new block reference
If blkRecId <> ObjectId.Null Then
Dim acBlkTblRec As BlockTableRecord
acBlkTblRec = acTrans.GetObject(blkRecId, OpenMode.ForRead)
Using acBlkRef As New BlockReference(New Point3d(5, 5, 0), acBlkTblRec.Id)
Dim acCurSpaceBlkTblRec As BlockTableRecord
acCurSpaceBlkTblRec = acTrans.GetObject(acCurDb.CurrentSpaceId, OpenMode.ForWrite)
acCurSpaceBlkTblRec.AppendEntity(acBlkRef)
acTrans.AddNewlyCreatedDBObject(acBlkRef, True)
' Verify block table record has attribute definitions associated with it
If acBlkTblRec.HasAttributeDefinitions Then
' Add attributes from the block table record
For Each objID As ObjectId In acBlkTblRec
Dim dbObj As DBObject = acTrans.GetObject(objID, OpenMode.ForRead)
If TypeOf dbObj Is AttributeDefinition Then
Dim acAtt As AttributeDefinition = dbObj
If Not acAtt.Constant Then
Using acAttRef As 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)
End Using
End If
End If
Next
' Display the tags and values of the attached attributes
Dim strMessage As String = ""
Dim attCol As AttributeCollection = acBlkRef.AttributeCollection
For Each objID As ObjectId In attCol
Dim dbObj As DBObject = acTrans.GetObject(objID, OpenMode.ForRead)
Dim acAttRef As AttributeReference = dbObj
strMessage = strMessage & "Tag: " & acAttRef.Tag & vbCrLf & _
"Value: " & acAttRef.TextString & vbCrLf
' Change the value of the attribute
acAttRef.TextString = "NEW VALUE!"
Next
MsgBox("The attributes for blockReference " & acBlkRef.Name & " are: " & vbCrLf & strMessage)
strMessage = ""
For Each objID As ObjectId In attCol
Dim dbObj As DBObject = acTrans.GetObject(objID, OpenMode.ForRead)
Dim acAttRef As AttributeReference = dbObj
strMessage = strMessage & "Tag: " & acAttRef.Tag & vbCrLf & _
"Value: " & acAttRef.TextString & vbCrLf
Next
MsgBox("The attributes for blockReference " & acBlkRef.Name & " are: " & vbCrLf & strMessage)
End If
End Using
End If
' Save the new object to the database
acTrans.Commit()
' Dispose of the transaction
End Using
End Sub
using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Geometry;
[CommandMethod("GettingAttributes")]
public void GettingAttributes()
{
// Get the current database and start a transaction
Database acCurDb;
acCurDb = Application.DocumentManager.MdiActiveDocument.Database;
using (Transaction acTrans = acCurDb.TransactionManager.StartTransaction())
{
// Open the Block table for read
BlockTable acBlkTbl;
acBlkTbl = acTrans.GetObject(acCurDb.BlockTableId, OpenMode.ForRead) as BlockTable;
ObjectId blkRecId = ObjectId.Null;
if (!acBlkTbl.Has("TESTBLOCK"))
{
using (BlockTableRecord acBlkTblRec = new BlockTableRecord())
{
acBlkTblRec.Name = "TESTBLOCK";
// Set the insertion point for the block
acBlkTblRec.Origin = new Point3d(0, 0, 0);
// Add an attribute definition to the block
using (AttributeDefinition acAttDef = new AttributeDefinition())
{
acAttDef.Position = new Point3d(5, 5, 0);
acAttDef.Prompt = "Attribute Prompt";
acAttDef.Tag = "AttributeTag";
acAttDef.TextString = "Attribute Value";
acAttDef.Height = 1;
acAttDef.Justify = AttachmentPoint.MiddleCenter;
acBlkTblRec.AppendEntity(acAttDef);
acBlkTbl.UpgradeOpen();
acBlkTbl.Add(acBlkTblRec);
acTrans.AddNewlyCreatedDBObject(acBlkTblRec, true);
}
blkRecId = acBlkTblRec.Id;
}
}
else
{
blkRecId = acBlkTbl["CircleBlockWithAttributes"];
}
// Create and insert the new block reference
if (blkRecId != ObjectId.Null)
{
BlockTableRecord acBlkTblRec;
acBlkTblRec = acTrans.GetObject(blkRecId, OpenMode.ForRead) as BlockTableRecord;
using (BlockReference acBlkRef = new BlockReference(new Point3d(5, 5, 0), acBlkTblRec.Id))
{
BlockTableRecord acCurSpaceBlkTblRec;
acCurSpaceBlkTblRec = acTrans.GetObject(acCurDb.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);
}
}
}
}
// Display the tags and values of the attached attributes
string strMessage = "";
AttributeCollection attCol = acBlkRef.AttributeCollection;
foreach (ObjectId objID in attCol)
{
DBObject dbObj = acTrans.GetObject(objID, OpenMode.ForRead) as DBObject;
AttributeReference acAttRef = dbObj as AttributeReference;
strMessage = strMessage + "Tag: " + acAttRef.Tag + "\n" +
"Value: " + acAttRef.TextString + "\n";
// Change the value of the attribute
acAttRef.TextString = "NEW VALUE!";
}
Application.ShowAlertDialog("The attributes for blockReference " + acBlkRef.Name + " are:\n" + strMessage);
strMessage = "";
foreach (ObjectId objID in attCol)
{
DBObject dbObj = acTrans.GetObject(objID, OpenMode.ForRead) as DBObject;
AttributeReference acAttRef = dbObj as AttributeReference;
strMessage = strMessage + "Tag: " + acAttRef.Tag + "\n" +
"Value: " + acAttRef.TextString + "\n";
}
Application.ShowAlertDialog("The attributes for blockReference " + acBlkRef.Name + " are:\n" + strMessage);
}
}
}
// Save the new object to the database
acTrans.Commit();
// Dispose of the transaction
}
}
Sub GettingAttributes()
' Create the block
Dim blockObj As AcadBlock
Dim insertionPnt(0 To 2) As Double
insertionPnt(0) = 0
insertionPnt(1) = 0
insertionPnt(2) = 0
Set blockObj = ThisDrawing.Blocks.Add(insertionPnt, "TESTBLOCK")
' Define the attribute definition
Dim attributeObj As AcadAttribute
Dim height As Double
Dim mode As Long
Dim prompt As String
Dim insertionPoint(0 To 2) As Double
Dim tag As String
Dim value As String
height = 1
prompt = "Attribute Prompt"
insertionPoint(0) = 5
insertionPoint(1) = 5
insertionPoint(2) = 0
tag = "AttributeTag"
value = "Attribute Value"
' Create the attribute definition object on the block
Set attributeObj = blockObj.AddAttribute(height, mode, prompt, insertionPoint, tag, value)
' Insert the block
Dim blockRefObj As AcadBlockReference
insertionPnt(0) = 2
insertionPnt(1) = 2
insertionPnt(2) = 0
Set blockRefObj = ThisDrawing.ModelSpace.InsertBlock(insertionPnt, "TESTBLOCK", 1, 1, 1, 0)
' Get the attributes for the block reference
Dim varAttributes As Variant
varAttributes = blockRefObj.GetAttributes
' Move the attribute tags and values into a
' string to be displayed in a Msgbox
Dim strAttributes As String
strAttributes = ""
Dim I As Integer
For I = LBound(varAttributes) To UBound(varAttributes)
strAttributes = strAttributes + " Tag: " + _
varAttributes(I).TagString + vbCrLf + _
" Value: " + varAttributes(I).textString
Next
MsgBox "The attributes for blockReference " + _
blockRefObj.Name & " are: " & vbCrLf & strAttributes
' Change the value of the attribute
' Note: There is no SetAttributes. Once you have the
' variant array, you have the objects.
' Changing them changes the objects in the drawing.
varAttributes(0).textString = "NEW VALUE!"
' Get the attributes again
Dim newvarAttributes As Variant
newvarAttributes = blockRefObj.GetAttributes
' Again, display the tags and values
strAttributes = ""
For I = LBound(varAttributes) To UBound(varAttributes)
strAttributes = strAttributes + " Tag: " + _
newvarAttributes(I).TagString + vbCrLf + _
" Value: " + newvarAttributes(I).textString
Next
MsgBox "The attributes for blockReference " & _
blockRefObj.Name & " are: " & vbCrLf & strAttributes
End Sub