本文演示Revit中创建尺寸标注。

using Autodesk.Revit.Attributes;
using Autodesk.Revit.DB;
using Autodesk.Revit.UI;
using Autodesk.Revit.UI.Selection;
using System;

namespace RevitAddin4
{
    [TransactionAttribute(TransactionMode.Manual)]
    public class RevitAddin : IExternalCommand
    {
        public Result Execute(ExternalCommandData commandData, ref string message, ElementSet elements)
        {
            UIDocument uiDoc = commandData.Application.ActiveUIDocument;
            Document doc = uiDoc.Document;
            Selection selection = uiDoc.Selection;
            //选择待标注的对象
            Reference reference1 = selection.PickObject(ObjectType.PointOnElement);
            Reference reference2 = selection.PickObject(ObjectType.PointOnElement);
            ReferenceArray refArray = new ReferenceArray();
            refArray.Append(reference1);
            refArray.Append(reference2);
            Element element = doc.GetElement(reference1);
            Line line = element.GetGeometryObjectFromReference(reference1) as Line;         
            if (line == null)
            {
                TaskDialog.Show("错误", "不是line");
                return Result.Failed;
            }
            //旋转90度，作为尺寸标注线
            double dir = Math.Acos(line.Direction.X) + Math.PI / 2;
            Line dirLine = Line.CreateUnbound(line.Origin, new XYZ(Math.Cos(dir), Math.Sin(dir), 0));
            //在事务中创建尺寸标注线
            using (Transaction tr = new Transaction(doc))
            {
                tr.Start("Create detail curve");
                doc.Create.NewDimension(doc.ActiveView, dirLine, refArray);
                tr.Commit();
            }         
            return Result.Succeeded;
        }
    }
}

    执行结果：