Возникает ошибка при работе программы

Imports Autodesk.AutoCAD.ApplicationServices
Imports Autodesk.AutoCAD.DatabaseServices
Imports Autodesk.AutoCAD.EditorInput
Imports Autodesk.AutoCAD.Geometry
Imports Autodesk.AutoCAD.Runtime



Public Class UserForm2

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Me.Hide()
        '' Get the current database and start the Transaction Manager
        Dim acDoc As Document = Application.DocumentManager.MdiActiveDocument
        Dim acCurDb As Database = acDoc.Database

        Dim pPtRes As PromptPointResult
        Dim pPtOpts As PromptPointOptions = New PromptPointOptions("")

        '' Prompt for the start point
        pPtOpts.Message = vbLf & "Enter the start point of the line: "
        pPtRes = acDoc.Editor.GetPoint(pPtOpts)
        Dim ptStart As Point3d = pPtRes.Value

        '' Exit if the user presses ESC or cancels the command
        If pPtRes.Status = PromptStatus.Cancel Then Exit Sub

        '' Prompt for the end point
        pPtOpts.Message = vbLf & "Enter the end point of the line: "
        pPtOpts.UseBasePoint = True
        pPtOpts.BasePoint = ptStart
        pPtRes = acDoc.Editor.GetPoint(pPtOpts)
        Dim ptEnd As Point3d = pPtRes.Value

        If pPtRes.Status = PromptStatus.Cancel Then Exit Sub

        '' Start a transaction
        Using acTrans As Transaction = acCurDb.TransactionManager.StartTransaction()

            Dim acBlkTbl As BlockTable
            Dim acBlkTblRec As BlockTableRecord

            '' Open Model space for write
            acBlkTbl = acTrans.GetObject(acCurDb.BlockTableId, _
                                         OpenMode.ForRead)

            acBlkTblRec = acTrans.GetObject(acBlkTbl(BlockTableRecord.ModelSpace), _
                                            OpenMode.ForWrite)

            '' Define the new line
            Dim acLine As Line = New Line(ptStart, ptEnd)
            acLine.SetDatabaseDefaults()

            '' Add the line to the drawing
            acBlkTblRec.AppendEntity(acLine)
            acTrans.AddNewlyCreatedDBObject(acLine, True)

            '' Zoom to the extents or limits of the drawing
            acDoc.SendStringToExecute("._zoom _all ", True, False, False)

            '' Commit the changes and dispose of the transaction
            acTrans.Commit()
        End Using



    End Sub
End Class