需要幫助C＃錯誤：未將對象引用設置到對象的實例

Question

你能不能幫我解決以下錯誤消息：

"Object reference not set to an instance of an object."

我標誌着區域我得到的錯誤意見和**

請參閱下文。

private static void _GenerateWord(string fname, string reportStartDate, string reportEndDate) 
     { 
      var word = new Microsoft.Office.Interop.Word.Application(); 
      var doc = new Microsoft.Office.Interop.Word.Document(); 
      word.Visible = false; 
      object missing = Type.Missing; 

      object fileName = (@LetterTemplateLocation + LetterName); 

      doc = word.Documents.Open(ref fileName); 


      doc.Activate();//**Error message here "Object reference not set to an instance of an object."** 

      string dateWithFormat = DateTime.Now.ToString("MMMM d, yyyy"); 

      //**Error message here "Object reference not set to an instance of an object."** 
      foreach (Microsoft.Office.Interop.Word.Range tmpRange in doc.StoryRanges) 
      { 
       _FindAndReplace("<date>", dateWithFormat, tmpRange, missing); 

       _FindAndReplace("<filename>", fname, tmpRange, missing); 

       _FindAndReplace("<startdate>", reportStartDate, tmpRange, missing); 

       _FindAndReplace("<enddate>", reportEndDate, tmpRange, missing); 
      } 

      if (doc != null) 
      { 
       doc.Close(ref missing, ref missing, ref missing); 
       word.Application.Quit(ref missing, ref missing, ref missing); 
      } 
     } 

謝謝。

Answer 1

作爲一個實踐需要檢查文檔爲null。

If(doc !=null){...}

還需要評估其他人建議的有效文件。