❌ 匯出發生錯誤：<br>Object cannot be cast from DBNull to other types.<br><pre>   at System.DBNull.System.IConvertible.ToInt32(IFormatProvider provider)
   at e_Learning2025.Controllers.StatisticsController.ExportElearning() in D:\000_WebCode\022server\e-learning2025\e-learning2025\e-learning2025\Controllers\StatisticsController.cs:line 159</pre>