A collection of Civil 3D API utility methods

Table of Contents

Motivation
The template for CommandMethod
The extension methods

This post is inspired by Autodesk employee @mooglam, who has always been very helpful — thank you!

Motivation #

This is written for the following people:

My future self, when I need to post an API question on the Autodesk Civil 3D forum. I can simply link to this post as a supplement to my question.
Autodesk developers who have the (mis)fortune of investigating my queries or bug reports, so they don’t have to fill in the gaps themselves.
Other Civil 3D developers looking to add some utility methods to their repertoire.

The template for `CommandMethod` #

This is the core of the method. It contains the code whose behavior I want to illustrate:

   public class Cmd
    {
        private static CivilDocument CivilDoc => CivilApplication.ActiveDocument;

        private static void Transact(Action<Transaction> action)
        {
            var doc = Application.DocumentManager.MdiActiveDocument;
            using var tr = doc.TransactionManager.StartTransaction();
            action(tr);
            tr.Commit();
        }
        [CommandMethod(nameof(YourMethod))]
        public void YourMethod()
        {
              Transact(()=>
              {
                      // add your method here
              }
              );
              
        }
   }

The extension methods #

This is the helper methods that make the main code more readable and succinct.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.EditorInput;
using Autodesk.AutoCAD.Runtime;
using Autodesk.Civil.ApplicationServices;
using Autodesk.Civil.DatabaseServices;
using DBObject = Autodesk.AutoCAD.DatabaseServices.DBObject;

    public static class CivilUtilsExtensions
    {
        public static T GetObject<T>(this Transaction ts, ObjectId objectId, OpenMode mode = OpenMode.ForRead)
            where T : DBObject
        {
            return ts != null && !objectId.IsNull
                ? ts.GetObject(objectId, mode) as T
                : null;
        }

        public static T FirstOrDefaultEntity<T>(this ObjectIdCollection ids, Transaction ts, OpenMode mode = OpenMode.ForRead)
            where T : DBObject
            => ids.FirstOrDefaultEntity<T>(ts, mode, (t) => true);

        public static T FirstOrDefaultEntity<T>(this ObjectIdCollection ids, Transaction ts, OpenMode mode, Func<T, bool> filter)
            where T : DBObject
            => ids?.Cast<ObjectId>().FirstOrDefaultEntity(ts, mode, filter);

        public static T FirstOrDefaultEntity<T>(this IEnumerable<ObjectId> ids, Transaction ts, OpenMode mode, Func<T, bool> filter)
            where T : DBObject
        {
            if (ids == null || ts == null || filter == null) return null;

            foreach (var id in ids)
            {
                var obj = ts.GetObject<T>(id, mode);
                if (obj != null && filter(obj))
                    return obj;
            }
            return null;
        }

        public static T SingleEntity<T>(this ObjectIdCollection ids, Transaction ts, Func<T, bool> predicate)
            where T : DBObject
        {
            return ids?
                .Cast<ObjectId>()
                .Select(id => ts.GetObject<T>(id))
                .Where(obj => obj != null)
                .SingleOrDefault(predicate);
        }
    }