C#与EXCEL交互出现问题

Question

学习CAD二开需要与EXCEL交互，从Nuget下了netOffice库。
学习到以下代码，但是总是出错，不知道怎么处理，错误在
“Excel.Worksheet sheet =(Excel.Worksheet) book.Worksheets[1];”这一行，
错误的原因：NetOffice.NetOfficeException:“Factory is not initialized with NetOffice assemblies.”

using Autodesk.AutoCAD.Runtime;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Excel = NetOffice.ExcelApi;

namespace _02创建图形
{
    public  class ExcelDemo
    {
        [CommandMethod("ExtToExcelDemo")]
        public void ExtToExcelDemo()
        {            
            Excel.Application excelApp = new Excel.Application();
            Excel.Workbook book = excelApp.Workbooks.Add();
            Excel.Worksheet sheet =(Excel.Worksheet) book.Worksheets[1];
            sheet.Cells[1, 1].Value = "吸湿性";
            book.Save();
            excelApp.Quit();
            excelApp.Dispose();
        }
    }
}

Answer 1

百度搜“NetOffice.NetOfficeException:“Factory is not initialized with NetOffice assemblies.””