Basic Examples for Getting Started with CAD Custom Development

Here are some simple examples of CAD secondary development:

1. Hello World
2. Draw a circle
3. Draw a straight line
4. Get all object IDs on a specific layer
5. Get the IDs of all objects on the current layer
6. Retrieve all current layer names
7. Add a new layer

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.Windows;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Geometry;
using Autodesk.AutoCAD.Colors;
using Autodesk.AutoCAD.EditorInput;
using System.Collections;
using AcadApp = Autodesk.AutoCAD.ApplicationServices.Application;
using System.Reflection;

namespace CADDevelopment
{
    public class Class1
    {
        /// <summary>
        /// Prints "Hello World" in the AutoCAD editor
        /// </summary>
        [CommandMethod("HelloWorld")]
        public void HelloWorld()
        {
            Editor ed = AcadApp.DocumentManager.MdiActiveDocument.Editor;
            ed.WriteMessage("Hello World222");
        }

        /// <summary>
        /// Draws a circle in the model space
        /// </summary>
        [CommandMethod("test")]
        public void CreateCircle()
        {
            // Declare the circle object
            Circle circle;

            // To add a circle, we need to access model space through BlockTable and BlockTableRecord
            BlockTableRecord btr;
            BlockTable bt;

            // Use a Transaction to manage database operations
            Transaction trans;

            // Start a transaction
            trans = HostApplicationServices.WorkingDatabase.TransactionManager.StartTransaction();

            // Create a circle at point (10,10,0) with radius 2 and normal vector along Z axis
            circle = new Circle(new Point3d(10, 10, 0), Vector3d.ZAxis, 2);

            // Get the block table for read access
            bt = (BlockTable)trans.GetObject(HostApplicationServices.WorkingDatabase.BlockTableId, OpenMode.ForRead);

            // Open the current space for write access to add the circle
            btr = (BlockTableRecord)trans.GetObject(HostApplicationServices.WorkingDatabase.CurrentSpaceId, OpenMode.ForWrite);

            // Append the circle entity and notify the transaction
            btr.AppendEntity(circle);
            trans.AddNewlyCreatedDBObject(circle, true);

            // Commit and dispose the transaction
            trans.Commit();
            trans.Dispose();
        }

        /// <summary>
        /// Select a point and display its coordinates; then select two points and display their distance
        /// </summary>
        [CommandMethod("selectPoint")]
        public void SelectPoint()
        {
            Editor ed = AcadApp.DocumentManager.MdiActiveDocument.Editor;

            // Prompt user to select a point
            PromptPointOptions prPointOptions = new PromptPointOptions("Select a point");
            PromptPointResult prPointRes = ed.GetPoint(prPointOptions);

            if (prPointRes.Status != PromptStatus.OK)
            {
                ed.WriteMessage("Error");
                return;
            }
            ed.WriteMessage("You selected point: " + prPointRes.Value.ToString());

            // Prompt user to select two points to find distance
            PromptDistanceOptions prDistOptions = new PromptDistanceOptions("Find distance, select first point:");
            PromptDoubleResult prDistRes = ed.GetDistance(prDistOptions);

            if (prDistRes.Status != PromptStatus.OK)
            {
                ed.WriteMessage("Error");
                return;
            }
            ed.WriteMessage("The distance is: " + prDistRes.Value.ToString());
        }

        [CommandMethod("CreateDivision")]
        public void CreateDivision()
        {
            Database db = HostApplicationServices.WorkingDatabase;
            Transaction trans = db.TransactionManager.StartTransaction();
            try
            {
                // Get the Named Objects Dictionary for write access
                DBDictionary NOD = (DBDictionary)trans.GetObject(db.NamedObjectsDictionaryId, OpenMode.ForWrite);

                DBDictionary acmeDict;

                try
                {
                    // Try to get the "ACME_DIVISION" dictionary
                    acmeDict = (DBDictionary)trans.GetObject(NOD.GetAt("ACME_DIVISION"), OpenMode.ForRead);
                }
                catch
                {
                    // If not found, create it and add to NOD
                    acmeDict = new DBDictionary();
                    NOD.SetAt("ACME_DIVISION", acmeDict);
                    trans.AddNewlyCreatedDBObject(acmeDict, true);
                }

                trans.Commit();
            }
            finally
            {
                trans.Dispose();
            }
        }

        /// <summary>
        /// Draws a straight line between two points
        /// </summary>
        [CommandMethod("FirstLine")]
        public static void FirstLine()
        {
            Database db = HostApplicationServices.WorkingDatabase;

            using (Transaction trans = db.TransactionManager.StartTransaction())
            {
                BlockTable acBlkTbl = trans.GetObject(db.BlockTableId, OpenMode.ForRead) as BlockTable;

                // Open the model space block table record for write
                BlockTableRecord acBlkTblRec = trans.GetObject(acBlkTbl[BlockTableRecord.ModelSpace], OpenMode.ForWrite) as BlockTableRecord;

                Point3d startPoint = new Point3d(0, 100, 0);
                Point3d endPoint = new Point3d(100, 100, 0);

                // Create a new line object
                Line line = new Line(startPoint, endPoint);

                // Add the line to the block table record and to the transaction
                acBlkTblRec.AppendEntity(line);
                trans.AddNewlyCreatedDBObject(line, true);

                // Commit the transaction to save changes
                trans.Commit();
            }
        }

        #region Get all object IDs on a specific layer
        /// <summary>
        /// Retrieves all object IDs on the specified layer
        /// </summary>
        /// <param name="name">Layer name</param>
        /// <returns>Collection of ObjectIds</returns>
        public ObjectIdCollection GetObjectIdsAtLayer(string name)
        {
            ObjectIdCollection ids = new ObjectIdCollection();
            PromptSelectionResult ProSset = null;

            TypedValue[] filList = new TypedValue[1] { new TypedValue((int)DxfCode.LayerName, name) };
            SelectionFilter sfilter = new SelectionFilter(filList);

            Editor ed = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument.Editor;
            ProSset = ed.SelectAll(sfilter);

            if (ProSset.Status == PromptStatus.OK)
            {
                SelectionSet sst = ProSset.Value;
                ObjectId[] oids = sst.GetObjectIds();

                foreach (ObjectId oid in oids)
                {
                    ids.Add(oid);
                }
            }
            return ids;
        }
        #endregion

        /// <summary>
        /// Retrieve IDs of all geometry on the current layer
        /// </summary>
        [CommandMethod("GetAllId")]
        public void GetAllId()
        {
            Editor ed = AcadApp.DocumentManager.MdiActiveDocument.Editor;

            ObjectIdCollection ids = GetObjectIdsAtLayer("0");
            string str = "";
            Database db = HostApplicationServices.WorkingDatabase;

            using (Transaction trans = db.TransactionManager.StartTransaction())
            {
                BlockTable acBlkTbl = trans.GetObject(db.BlockTableId, OpenMode.ForRead) as BlockTable;
                BlockTableRecord acBlkTblRec = trans.GetObject(acBlkTbl[BlockTableRecord.ModelSpace], OpenMode.ForWrite) as BlockTableRecord;

                foreach (ObjectId item in ids)
                {
                    Entity entity = (Entity)item.GetObject(OpenMode.ForRead, false, false);
                    if (entity.GetRXClass().Name == "AcDbText")
                    {
                        DBText dbtext = entity as DBText;
                        str += dbtext.TextString + 'n';
                    }
                }

                ed.WriteMessage(str);
                trans.Commit();
            }
        }

        #region Retrieve all current layer names
        /// <summary>
        /// Retrieves all layer names currently in the drawing
        /// </summary>
        /// <returns>A list of layer names</returns>
        [CommandMethod("GetAllLayer")]
        public ArrayList GetLayerName()
        {
            ArrayList layers = new ArrayList();

            using (Database db = HostApplicationServices.WorkingDatabase)
            {
                using (Transaction trans = db.TransactionManager.StartTransaction())
                {
                    using (LayerTable lt = (LayerTable)trans.GetObject(db.LayerTableId, OpenMode.ForRead))
                    {
                        foreach (ObjectId id in lt)
                        {
                            LayerTableRecord ltr = (LayerTableRecord)trans.GetObject(id, OpenMode.ForRead);
                            layers.Add(ltr.Name);
                        }
                    }
                    trans.Commit();
                }
            }
            return layers;
        }
        #endregion

        #region Add a new layer
        /// <summary>
        /// Adds a new layer or modifies an existing one
        /// </summary>
        /// <param name="layName">Name of the layer</param>
        /// <param name="layColor">Color index of the layer</param>
        private ObjectId AddLayer(string layName, short layColor)
        {
            ObjectId oidReturn = new ObjectId();

            using (Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument.LockDocument())
            {
                Database database = HostApplicationServices.WorkingDatabase;
                Editor editor = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument.Editor;

                using (Transaction transaction = database.TransactionManager.StartTransaction())
                {
                    try
                    {
                        ObjectId id;
                        LayerTable table = transaction.GetObject(database.LayerTableId, OpenMode.ForWrite) as LayerTable;
                        LayerTableRecord record = new LayerTableRecord();

                        if (table.Has(layName))
                        {
                            id = table.Id;
                            record = transaction.GetObject(id, OpenMode.ForWrite) as LayerTableRecord;
                            record.IsOff = false;
                            record.IsLocked = false;

                            if (id != database.Clayer)
                            {
                                record.IsFrozen = false;
                            }
                        }
                        else
                        {
                            record.Name = layName;
                            id = table.Add(record);
                            transaction.AddNewlyCreatedDBObject(record, true);
                        }

                        record.Color = Autodesk.AutoCAD.Colors.Color.FromColorIndex(ColorMethod.ByColor, layColor);
                        database.Clayer = id;
                        oidReturn = id;

                        transaction.Commit();
                    }
                    catch (Autodesk.AutoCAD.Runtime.Exception exception)
                    {
                        editor.WriteMessage("Error in AddLayer(): " + exception.Message);
                    }
                }
            }
            return oidReturn;
        }
        #endregion
    }
}

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