错误提示：
“System.IO.FileLoadException”类型的异常在 Utility.dll 中发生，但未在用户代码中进行处理

其他信息: 未能加载文件或程序集“NPOI, Version=2.4.0.0, Culture=neutral, PublicKeyToken=0df73ec7942b34e1”或它的某一个依赖项。找到的程序集清单定义与程序集引用不匹配。 (异常来自 HRESULT:0x80131040)

我的代码如下：

            FileInfo fi = new FileInfo(file.FileName);
            string houzui = fi.Extension;   //文件扩展名
            string dir = DateTime.Now.ToString("yyyyMMdd");
            string abpath = Server.MapPath($"/upload/{dir}/");

            if (!Directory.Exists(abpath))
            {
                Directory.CreateDirectory(abpath);
            }
            string slt = Server.MapPath($"/upload/{dir}/slt/");
            if (!Directory.Exists(slt))
            {
                Directory.CreateDirectory(slt);
            }
            string newname = Guid.NewGuid().ToString().Substring(0, 6) + houzui;
            file.SaveAs(abpath + newname);
            string physicalPath = abpath + newname;
            DataTable dt = Tool.RenderDataTableFromExcel(physicalPath);



    public static DataTable RenderDataTableFromExcel(string path)
    {
        DataTable dt = new DataTable();

        HSSFWorkbook hssfworkbook;
        using (FileStream file = new FileStream(path, FileMode.Open, FileAccess.Read))
        {
            hssfworkbook = new HSSFWorkbook(file);
        }
        HSSFSheet sheet = (HSSFSheet)hssfworkbook.GetSheetAt(0);
        System.Collections.IEnumerator rows = sheet.GetRowEnumerator();

        HSSFRow headerRow = (HSSFRow)sheet.GetRow(0);
        int cellCount = headerRow.LastCellNum;

        for (int j = 0; j < cellCount; j++)
        {
            HSSFCell cell = (HSSFCell)headerRow.GetCell(j);
            if (cell == null)
            {
                dt.Columns.Add("");
            }
            else
            {
                dt.Columns.Add(cell.ToString());
            }
        }

        for (int i = (sheet.FirstRowNum + 1); i <= sheet.LastRowNum; i++)
        {
            HSSFRow row = (HSSFRow)sheet.GetRow(i);

            if (row == null)
            {
                continue;
            }
            DataRow dataRow = dt.NewRow();

            for (int j = row.FirstCellNum; j < cellCount; j++)
            {
                if (row.GetCell(j) != null)
                    dataRow[j] = row.GetCell(j).ToString();
            }

            dt.Rows.Add(dataRow);
        }
        return dt;
    }