C#.Net: Circle All MText Objects in a Drawing

This program places a red circle around all MText objects in a drawing. The functionality is pretty much stripped down to a basic starting point. This should be a fun program to add additional features to in order to continue exploring C#.Net concepts.

The inline comments should explain each segment, a few things to point out are:

• We use two functions - one as our entry point with the AutoCAD defined command, and the other as a support function called by the main one.
• We use some of the provided object methods from the AutoCAD API. For example, as we work with an MText object we use the predefined Location method to determine the coordinates.

Some of the features we will add on in future posts can be:

• Prompt options to allow the user to change the circle color, size, etc.
• Place circles around Text objects as well as MText.
• Place circles around Text/MText objects that match a string provided by the user.

Here is the C# code:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using Autodesk.AutoCAD.Runtime;

using Autodesk.AutoCAD.ApplicationServices;

using Autodesk.AutoCAD.DatabaseServices;

using Autodesk.AutoCAD.EditorInput;

using Autodesk.AutoCAD.Geometry;

namespace SLD

{

    public class SLDtools

    {

        [CommandMethod("SLDcirText")]

        public void SLDcirText()

        {

            //get current document

            Document acDoc =

                Application.DocumentManager.MdiActiveDocument;

            //get AutoCAD database

            Database acCurDb = acDoc.Database;

            //start db transaction

            using (Transaction acTrans =

                acCurDb.TransactionManager.StartTransaction())

            {

                //open block table

                /*all drawing objects are in the block table so in

                 order to look at each object we need to have the

                 block table open for read*/

                BlockTable bt = (BlockTable)acTrans.GetObject

                    (acCurDb.BlockTableId, OpenMode.ForRead);

                BlockTableRecord btr = (BlockTableRecord)

                    acTrans.GetObject(bt[BlockTableRecord.ModelSpace],

                    OpenMode.ForRead);

                //iterate through block table to locate mtext objects

                /*this foreach loop will loop through the block table

                 record looking at each object in the drawing.*/

                foreach (ObjectId id in btr)

                {

                    //open each object to read

                    DBObject obj = acTrans.GetObject

                        (id, OpenMode.ForRead);

                    //only deal with MText objects

                    MText dbMText = obj as MText;

                    //if current object is Mtext then draw a circle

                    //around it

                    if (dbMText != null)

                    {

                        //call separate function to draw circle

                        /*here we want to pass the acad db, the current

                         transaction, and the mtext object that we want

                         to draw a circle around*/

                        SLDdrawCir(acCurDb, acTrans, dbMText);

                    }

                }

                //commit the transaction so we do not leave the db open

                acTrans.Commit();

            }

        }

        //function to draw circle around an MText object

        public void SLDdrawCir(Database acCurDb,

            Transaction acTrans, MText MtextObj)

        {

            //define a new point object for the center point of circle

            Point3d cenPoint = new Point3d();

            //use the location method of the Mtext object to define

            //the center point coordinates

            cenPoint = MtextObj.Location;

            //define a new Circle object

            /*we use the center point defined above, assign a diameter

             and assign a color using the ColorIndex method from the

             circle object*/

            Circle textCir = new Circle();

            textCir.Center = cenPoint;

            textCir.Diameter = 1.0;

            textCir.ColorIndex = 1;

            //now add the circle to the drawing (model space)

            /*We need to add it to the block table, this is the same

             basic operations when adding geometry to a drawing*/

            BlockTable acBlkTbl;

            acBlkTbl = acTrans.GetObject(

                acCurDb.BlockTableId, OpenMode.ForRead) as BlockTable;

            BlockTableRecord acBlkTblRec;

            acBlkTblRec = acTrans.GetObject(

                acBlkTbl[BlockTableRecord.ModelSpace],

                OpenMode.ForWrite)

                as BlockTableRecord;

            acBlkTblRec.AppendEntity(textCir);

            acTrans.AddNewlyCreatedDBObject(textCir, true);

        }

    }

}

To test this build the solution and NETLOAD the .dll into AutoCAD. Place some MText objects in the drawing and then type in SLDcirText at the command line.