CODEWITHSUNDEEP
c#xmllinqlinq-to-xml
user1503496
user1503496

Reputation: 191

Exception C# null list

I am filling a list from an XML file. Some nodes may not exist and this causes an exception because it returns null. Here is the code: 

public static List<Compte> getXmlComptes(string pathXml)
{
    var doc = XDocument.Load(pathXml);
    var comptes = doc.Descendants("Anzeige").Descendants("Kunde").Descendants("Konto").Select(p => new Compte()
    {
        NumCompte = p.Element("KtoNr") != null ? p.Element("KtoNr").Value : String.Empty,
        typeCompte = p.Element("KontoArt") != null ? p.Element("KontoArt").Value : String.Empty,

        Trans = getXmlTransactions(pathXml)
    }).ToList();

    return comptes;
}

How can I make a controf before adding items to the list. Thank you.

exemple of the xml file : 

<Anzeige>
   <Kunde>
      <IdClient>ppp</IdClient>
      <Konto>
           <NumCompte>258</NumCompte>
           <Transaction>
                <idTrans>85555</idTrans>
                <type>blebleble</type>
           </Transaction>
           <Transaction>
                <idTrans>85555</idTrans>
                <type>blebleble</type>
           </Transaction>
       </Konto>
    </Kunde>
</Anzeige>

code of getXmlTransaction : 

public static List<Transaction> getXmlTransactions(string pathXml)
{
    var doc = XDocument.Load(pathXml);

    var transactions = doc.Descendants("Anzeige").Descendants("Kunde").Descendants("Konto").Descendants("Transaktion").Select(p => new Transaction()
        {
            TransID = p.Element("TransID") != null ? p.Element("TransID").Value : String.Empty,
            TypeTransaction = p.Element("TransArt") != null ? p.Element("TransArt").Value : String.Empty

        }).ToList();

    if (transactions != null)
        return transactions.ToList();
    else
        return new List<Transaction>();
}

Upvotes: 0

Views: 318

Answers (1)

Sergey Berezovskiy
Sergey Berezovskiy

Reputation: 236228

Use casting of element to string instead of reading it's value directly. If element was not found, you will have null string instead of exception:

var doc = XDocument.Load(pathXml);
var comptes = doc.Descendants("Anzeige")
                 .Descendants("Kunde")
                 .Descendants("Konto")
                 .Select(k => new Compte {
                     NumCompte = (string)k.Element("KtoNr"),
                     typeCompte = (string)k.Element("KontoArt"),
                     Trans = getXmlTransactions(k)
                  }).ToList();

If you want empty string instead of null when element not found, you can use null-coalescing operator

NumCompte = (string)p.Element("KtoNr") ?? ""

Use same technique for parsing nodes which may not exist. And I'm pretty sure that it's getXmlTransactions(pathXml) method throws exception.

UPDATE: Do not load whole xml document when you are getting transactions. How would you know which Konto element transactions to read. Pass Konto element instead and get its transactions:

public static List<Transaction> getXmlTransactions(XElement konto)
{
    return konto.Elements("Transaction")
                .Select(t => new Transaction {
                     TransID = (string)t.Element("idTrans"),
                     TypeTransaction = (string)t.Element("type")
                }).ToList();
}

NOTE: You have <idTrans> (instead TransID) and <type> (instead TransArt) elements in <Transaction> (instead Transaktion)! Also there is no KtoNr and KontoArt elements in your xml. Read element names carefully. Also instead of looking for all descendants it's better to search in direct children:

doc.Root.Elements("Kunde").Elements("Konto") ...

Upvotes: 3

Related Questions