1.新建项目

2.引用类库

3.修改属性

4.实现接口

using Bentley.MstnPlatformNET;
using System;
using System.Windows.Forms;

namespace _01HelloWorld {
    public class MyAddin : AddIn {
        public static MyAddin Addin = null;
        public MyAddin(IntPtr mdlDescriptor) : base(mdlDescriptor) {
            Addin = this;
        }

        protected override int Run(string[] commandLine) {
            MessageBox.Show("Hello World!");
            return 0;
        }
    }
}

5.生成并加装dll