Выбор текста с чертежа.

        <CommandMethod("chm")> _
        Public Sub ChangeTextInBlock()
            Dim doc As Document = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument
            Dim db As Database = doc.Database
            Dim ed As Editor = doc.Editor
            Dim oldstring As String = ed.GetString(vbLf + "Enter a string to find and replace: ").StringResult
            Dim newstring As String = ed.GetString(vbLf + "Enter a new string to replace with " + oldstring + " : ").StringResult
            
            Using trans As Transaction = db.TransactionManager.StartTransaction()
                Dim peo As PromptEntityOptions = New PromptEntityOptions(vbLf + "Select a Block: ")
                peo.SetRejectMessage("Selected object must be a type of BlockReference!")
                peo.AddAllowedClass(GetType(BlockReference), False)

                Dim res As PromptEntityResult = ed.GetEntity(peo)
                If res.Status <> PromptStatus.OK Then Return
                Dim dbo As DBObject = res.ObjectId.GetObject(OpenMode.ForRead, False, False)
                Dim bref As BlockReference = Nothing
                If dbo IsNot Nothing Then
                    bref = TryCast(dbo, BlockReference)
                End If
                Dim btr As BlockTableRecord
                btr = DirectCast(trans.GetObject(bref.BlockTableRecord, OpenMode.ForRead), BlockTableRecord)
                If btr.IsDynamicBlock Then
                    btr = DirectCast(trans.GetObject(bref.AnonymousBlockTableRecord, OpenMode.ForRead), BlockTableRecord)
                End If

                For Each id As ObjectId In btr
                    Dim obj As DBObject = DirectCast(trans.GetObject(id, OpenMode.ForRead), DBObject)
                    If TypeOf obj Is MText Then
                        Dim mtx As MText = TryCast(obj, MText)
                        If mtx.Contents = oldstring Then
                            btr.UpgradeOpen()
                            mtx.UpgradeOpen()
                            mtx.Contents = newstring
                            mtx.DowngradeOpen()
                            btr.DowngradeOpen()
                        End If
                        Exit For
                    End If
                Next
                trans.Commit()
                ed.Regen()

            End Using

        End Sub