AutoCAD -INSERT command in .NET

Question

I have been tasked with translating an AutoCAD plugin from VBA to VB.NET, and I'm currently a bit stuck.

The command I'm working on creates a new layer (or select it as the active layer if it already exist), then executes 2 "-INSERT" commands giving a point selected by the user, and a dwg-file. Then, the previous active layer is reset as the active layer.

The insert-command looks something like this:

-INSERT
C:\path\to\file.dwg
<point.x>,<point.y>,<point.z>
<documentScale>

Note: All the line-breaks in the command are added as vbCR (not vbCrLf).

My question is, how can I achieve the same result in .NET against ObjectARX? I can't use SendStringToExecute because it is async (with no callback), so in other words, I can't reset the current layer once it's done executing. There has to be some way to replicate this functionality in pure .NET code, probably using the BlockTable, but I have no idea how.

I've tried following the article found here: http://through-the-interface.typepad.com/through_the_interface/2006/08/import_blocks_f.html, but that had no visible effect on the document at all. I also tried to use myDatabase.Insert(transform, otherDatabase, False) and the command-prompt said something about blocks already existing and thus beeing skipped, yet I still saw no changes. I have no idea how much magic the "-INSERT" command actually does behind the scenes, but would it be viable to replicate it in .NET? Or is it somehow availible to be called as a normal method (not as a text-command sent to be processed by AutoCAD)?

Answer 1

The code example in the Through the Interface post, imports the blocks, but does not insert them into the drawing. You have to create a BlockReference and add it to the model space. It also inserts all the blocks from the file, not the file as a single block.

Here is the code I use to import a file as a whole block. This function returns a block reference you can insert into your drawing.

    Private Shared Function InsertFile(ByVal FileName as String, ByVal dwgdb As Database, ByVal tr As Transaction) As BlockReference

        Dim br As BlockReference
        Dim id As ObjectId

        'use a temporary database 
        Using TempDB As New Database(False, True)

            'Get block table
            Dim bt As BlockTable = tr.GetObject(dwgdb.BlockTableId, OpenMode.ForWrite, False)

            'Create unique block name
            Dim BlockName As String = FileName.Replace("\", "").Replace(":", "").Replace(".", "")

            'check if block already exists
            If Not bt.Has(BlockName) Then
                'check if file exists
                If IO.File.Exists(FileName) Then
                    'read in the file into the temp database
                    TempDB.ReadDwgFile(FileName, IO.FileShare.Read, True, Nothing)
                    'insert the tempdb into the current drawing db, id is the new block id
                    id = dwgdb.Insert(BlockName, TempDB, True)
                Else
                    'Throw exception for missing file 
                    Throw New System.Exception(String.Format("File {0} is not found for library item {1}", FileName, item.PartNo))
                End If

            Else
                id = bt.Item(BlockName)
            End If

            'create a new block reference
            br = New BlockReference(New Point3d(0, 0, 0), id)
        End Using

        Return br


    End Function

Here would be the example of using that function to insert a block into the file. In this example I use a jig, which allows the user to drop the object onto a location they want, otherwise you could just set the position.

      ' Get Editor
        Dim ed As Editor = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument.Editor
        ' Get Database
        Dim dwg As Database = ed.Document.Database

        'Lock document
        Using dl As DocumentLock = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument.LockDocument()

            '### Changed Try Finally to using, try was hiding errors
            'Begin Transaction
            Using trans As Transaction = dwg.TransactionManager.StartTransaction()

                Dim blockRef As BlockReference = InsertFile(FileName, dwg, trans)

                'check if layer exists/create
                AcadUtil.AcadFunctions.CheckLayer(LayerName, trans, dwg)
                blockRef.Layer = LayerName

                'set focus to the editor
                Autodesk.AutoCAD.Internal.Utils.SetFocusToDwgView()

                'have the user pick insert point
                Dim BlockMove As New AcadJigs.JigBlockMove(blockRef, False, 0)
                ed.Drag(BlockMove)
                'optionally you could just set the .Position of the block reference


                ' add it to the current space, first open the current space for write
                Dim btr As BlockTableRecord = trans.GetObject(dwg.CurrentSpaceId, OpenMode.ForWrite, True, True)

                ' Add block reference to current space
                btr.AppendEntity(blockRef)

                'Capture the handle
                handle = blockRef.Handle.Value.ToString

                ' remember to tell the transaction about the new block reference so that the transaction can autoclose it
                trans.AddNewlyCreatedDBObject(blockRef, True)

                'commit the transaction
                trans.Commit()

            End Using

        End Using

And here is also the CheckLayer function I called.

    Public Shared Sub CheckLayer(ByVal Name As String, ByVal tr As Transaction, ByVal dwg As Database)


        Dim lt As LayerTable = CType(tr.GetObject(dwg.LayerTableId, OpenMode.ForWrite), LayerTable)

        If lt.Has(Name) Then
            Return
        Else
            Dim ly As New LayerTableRecord
            ly.Name = Name
            lt.Add(ly)
            tr.AddNewlyCreatedDBObject(ly, True)
        End If

    End Sub

Just as a note, Kean's blog is a great resources, I pretty much learned all of the above code from there.

For completeness sake, here is the Jig class i reference in the insert code,

 Class JigBlockMove
        Inherits EntityJig

        Private _CenterPt As Point3d
        Private _ActualPoint As Point3d
        Private _LockZ As Boolean
        Private _Z As Double

        Public ReadOnly Property SelectedPoint() As Point3d
            Get
                Return _ActualPoint
            End Get
        End Property

        Public Sub New(ByVal BlockRef As BlockReference, ByVal LockZ As Boolean, ByVal Z As Double)
            MyBase.New(BlockRef)
            _CenterPt = BlockRef.Position
            _LockZ = LockZ
            _Z = Z
        End Sub

        Protected Overloads Overrides Function Sampler(ByVal prompts As JigPrompts) As SamplerStatus
            Dim jigOpts As New JigPromptPointOptions()
            jigOpts.UserInputControls = (UserInputControls.Accept3dCoordinates Or UserInputControls.NoZeroResponseAccepted Or UserInputControls.NoNegativeResponseAccepted)
            jigOpts.Message = vbLf & "Enter insert point: "
            Dim dres As PromptPointResult = prompts.AcquirePoint(jigOpts)
            If _ActualPoint = dres.Value Then
                Return SamplerStatus.NoChange
            Else
                _ActualPoint = dres.Value
            End If

            Return SamplerStatus.OK
        End Function

        Protected Overloads Overrides Function Update() As Boolean
            If _LockZ Then
                _CenterPt = New Point3d(_ActualPoint.X, _ActualPoint.Y, _Z)
            Else
                _CenterPt = _ActualPoint
            End If

            Try
                DirectCast(Entity, BlockReference).Position = _CenterPt
            Catch generatedExceptionName As System.Exception
                Return False
            End Try

            Return True
        End Function

        Public Function GetEntity() As Entity
            Return Entity
        End Function

    End Class

One note regarding working in .NET ObjectARX, there is a an issue with the single threaded nature of AutoCAD, and the fact that the .NET garbage collector runs on a separate thread. If you create any temporary AutoCAD objects that do not get added to the database, you must explicity call .Dispose() on them, or AutoCAD may crash! The crash will seem random too, since it will be triggered by the garbage collector thread. See this post, http://through-the-interface.typepad.com/through_the_interface/2008/06/cleaning-up-aft.html.