[求助]2009下面hello world怎么写？？

阿水被抢了

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.EditorInput;
using Autodesk.AutoCAD.Runtime;

namespace ClassLibrary1
{
    public class Class1
    {
        [CommandMethod("HelloWorld")]
        public void HelloWorld()
        {
            Editor ed = Application.DocumentManager.MdiActiveDocument.Editor;
            ed.WriteMessage("Hello World");
        }
    }
}

这样写不行，该怎么改，有人知道吗？？