任何人都可以幫助我處理以下代碼中的'system.nullreferenceexception'嗎？

Question

public FeeDetails GetFeeDetails(string admissionno) 
{ 
    var feedetails = from f in db.FeeDetails select f; 

    FeeDetails feedetail = feedetails.Where(f => f.AdmissionNo == admissionno).FirstOrDefault(); 
    FeeDetails feedetailfinal = new FeeDetails(); 

    feedetailfinal.Fee1 = feedetail.Fee1.ToString() != null ? Convert.ToInt32(feedetail.Fee1.ToString()) : 0; 
    feedetailfinal.Fee2 = feedetail.Fee2.ToString() != null ? Convert.ToInt32(feedetail.Fee2.ToString()) : 0; 
    feedetailfinal.Fee3 = feedetail.Fee3.ToString() != null ? Convert.ToInt32(feedetail.Fee3.ToString()) : 0; 
    feedetailfinal.Fee4 = feedetail.Fee4.ToString() != null ? Convert.ToInt32(feedetail.Fee4.ToString()) : 0; 
    feedetailfinal.Fee5 = feedetail.Fee5.ToString() != null ? Convert.ToInt32(feedetail.Fee5.ToString()) : 0; 


    return feedetailfinal; 
} 

Answer 1

我相信每個行應該是這樣的：

if(feedetail != null) 
{ 
    feedetailfinal.Fee1 = feedetail.Fee1 != null 
         ? Convert.ToInt32(feedetail.Fee1) 
         : 0; 
    //other lines 
}