public void UpdateTitleBlock()
        {
            Database db = HostApplicationServices.WorkingDatabase;
            Transaction trans;
            BlockTableRecord btr;
            BlockTable bt;
            BlockReference br;
            BlockTableRecord blkObj;
            Entity ent;

            //Editor ed = AcadApp.DocumentManager.MdiActiveDocument.Editor;

            using (Transaction trans = db.TransactionManager.StartTransaction())
            {
                try
                {
                    BlockTable bt = (BlockTable)trans.GetObject(db.BlockTableId, OpenMode.ForRead);
                    BlockTableRecord btr = (BlockTableRecord)trans.GetObject(bt[BlockTableRecord.PaperSpace], OpenMode.ForRead);
                    foreach (ObjectId bId in btr)
                    {
                        using (Entity ent = (Entity)trans.GetObject(bId, OpenMode.ForRead, false))
                        {

                            if (ent.GetRXClass().Name.ToString() == "AcDbBlockReference")
                            {

                                BlockReference br = (BlockReference)ent;

                                BlockTableRecord blkObj = (BlockTableRecord)trans.GetObject(br.BlockTableRecord, OpenMode.ForRead);

                                if ((blkObj.HasAttributeDefinitions) && (blkObj.Name == "TITLEBLK"))
                                {

                                    Autodesk.AutoCAD.DatabaseServices.AttributeCollection attcol = br.AttributeCollection;
                                    foreach (ObjectId attId in attcol)
                                    {
                                        AttributeReference attRef = (AttributeReference)trans.GetObject(attId, OpenMode.ForWrite);

                                        switch (attRef.Tag)
                                        {
                                            case "DWG_NO.":
                                                attRef.TextString = "My Number";
                                                break;
                                            case "SHEET_NUMBER":
                                                attRef.TextString = "My Sheet";
                                                break;
                                            case "REVISION_NUMBER":
                                                attRef.TextString = "My Rev";
                                                break;

                                        }

                                        string str = ("\n Updated  Attribute Tag: " + attRef.Tag + " Attribute String: " + attRef.TextString + "\n");
                                    }

                                }
                            }
                        }
                    } trans.Commit();
                }
                catch (System.Exception ex) { System.Windows.Forms.MessageBox.Show(ex.ToString()); MessageBox.Show("Unexpected Error: " + ex.ToString()); }
            }

        }


private void somefunction()
        {
            Database db = AcadApp.DocumentManager.MdiActiveDocument.WorkingDatabase;

            Editor ed = AcadApp.DocumentManager.MdiActiveDocument.Editor;

            using (Transaction trans = db.TransactionManager.StartTransaction())
            {
                try
                {
                    BlockTable bt = (BlockTable)trans.GetObject(db.BlockTableId, OpenMode.ForRead);
                    BlockTableRecord btr = (BlockTableRecord)trans.GetObject(bt[BlockTableRecord.PaperSpace], OpenMode.ForRead);
                    foreach (ObjectId bId in btr)
                    {
                        using (Entity ent = (Entity)trans.GetObject(bId, OpenMode.ForRead, false))
                        {

                            if (ent.GetRXClass().Name.ToString() == "AcDbBlockReference")
                            {

                                BlockReference br = (BlockReference)ent;

                                BlockTableRecord blkObj = (BlockTableRecord)trans.GetObject(br.BlockTableRecord, OpenMode.ForRead);

                                if ((blkObj.HasAttributeDefinitions) && (blkObj.Name == "TITLEBLK"))
                                {

                                    Autodesk.AutoCAD.DatabaseServices.AttributeCollection attcol = br.AttributeCollection;
                                    foreach (ObjectId attId in attcol)
                                    {
                                        AttributeReference attRef = (AttributeReference)trans.GetObject(attId, OpenMode.ForWrite);

                                        switch (attRef.Tag)
                                        {
                                            case "DWG_NO.":
                                                attRef.TextString = "My Number";
                                                break;
                                            case "SHEET_NUMBER":
                                                attRef.TextString = "My Sheet";
                                                break;
                                            case "REVISION_NUMBER":
                                                attRef.TextString = "My Rev";
                                                break;

                                        }

                                        string str = ("\n Updated  Attribute Tag: " + attRef.Tag + " Attribute String: " + attRef.TextString + "\n");
                                        ed.WriteMessage(str);
                                    }

                                }
                            }
                        }
                    } trans.Commit();
                }
                catch (System.Exception ex) {
                    ed.WriteMessage("Unexpected Error: " + ex.ToString());
                }
            }

       }