Getting xml node values try using SelectSingleNode and SelectNodes using c#

Question

In my application I want to get the value of an xml node display in a textbox if the user type in a number in another textbox (for example: User type in textbox1 the number "123". The application should check the xml if "123" exists and then gets the value of the other nodes). But the xml file isn't fixed. It's created by the application itself (what user types in textboxes).

After hours I still don't get it. It sounds very simple (and I be sure for most of you it is) but I'm a big newbie in c#. So I googled a lot and finally found SelectSingleNode and SelectNodes. First I tried this code:

private void txtKNrNew_Leave(object sender, EventArgs e)
{
    XDocument xdoc = XDocument.Load(path + "\\save.xml");
    int CustNos;

    if (Int32.TryParse(txtKNrNew.Text, out CustNos))
    {
        XmlDocument xmlDoc = new XmlDocument();
        xmlDoc.Load(path + "\\save.xml");

        var xmlNodeExist = "Buchhaltung/Customers/CustNo";
        var CustNoExist = xdoc.XPathSelectElements(xmlNodeExist).FirstOrDefault(x => (int)x == CustNos);

        var SurnameNode = xmlDoc.SelectSingleNode("Buchhaltung/Customers/Surname");
        var ForenameNode = xmlDoc.SelectSingleNode("Buchhaltung/Customers/Forename");
        string surname = SurnameNode.InnerText;
        string forename = ForenameNode.InnerText;

        if (CustNoExist != null)
        {
            txtSurnameNew.Text = surname;
            txtForenameNew.Text = forename;
        }
    }
}

This always returns me the values of the first xml nodes (Here: "Stuff" and "Thing". At the end you can see the XML file). So I tried using SelectNodes:

private void txtKNrNew_Leave(object sender, EventArgs e)
{
    XDocument xdoc = XDocument.Load(path + "\\save.xml");
    int CustNos;

    if (Int32.TryParse(txtKNrNew.Text, out CustNos))
    {
        XmlDocument xmlDoc = new XmlDocument();
        xmlDoc.Load(path + "\\save.xml");

        var xmlNodeExist = "Buchhaltung/Customers/CustNo";
        var CustNoExist = xdoc.XPathSelectElements(xmlNodeExist).FirstOrDefault(x => (int)x == CustNos);

        var SurnameNode = xmlDoc.SelectNodes("Buchhaltung/Customers/Surname");
        var ForenameNode = xmlDoc.SelectNodes("Buchhaltung/Customers/Forename");
        string surname = SurnameNode[0].InnerText;
        string forename = ForenameNode[0].InnerText;

        if (CustNoExist != null)
        {
            txtSurnameNew.Text = surname;
            txtForenameNew.Text = forename;
        }
    }
}

This returns me the same as the other one. I know because I use [0]. So the number in [] should not be fixed. But is there a way to do this not fixed? And which way is the better way to do this? How can I get the values correctly like I want?

Can someone please help me or give me a hint?

Thanks, Tyler

PS: And here you can see my generated XML file:

<Buchhaltung>
  <Customers>
    <CustNo>123</CustNo>
    <Surname>Stuff</Surname>
    <Forename>Thing</Forename>
    <Addr>Addr</Addr>
    <Zip>Zip</Zip>
    <Place>Place</Place>
    <Phone>Phone</Phone>
    <Mail>Mail</Mail>
  </Customers>
  <Customers>
    <CustNo>137</CustNo>
    <Surname>Other</Surname>
    <Forename>Name</Forename>
    <Addr>Address</Addr>
    <Zip>12345</Zip>
    <Place>New York</Place>
    <Phone>1234567890</Phone>
    <Mail>mail@example.com</Mail>
  </Customers>
</Buchhaltung>

Answer 1

You can use the following XPath-expression:

var expression = String.Format("//Customers[CustNo/text() = {0}]/", CustNos);

var SurnameNode = xmlDoc.SelectNodes(expression + "Surname");
var ForenameNode = xmlDoc.SelectNodes(expression +"Forename");

Answer 2

You can use LINQ2XML

XDocument doc=XDocument.Load(path);
var node=doc.Elements("Customers")
            .SingleOrDefault(x=>x.Element("CustNo").Value==CustNos.ToString());
if(node!=null)
{
   txtSurnameNew.Text=node.Element("Surname").Value;
   txtForenameNew.Text=node.Element("Forename").Value;
}

Answer 3

How about that:

XmlDocument xmlDoc = new XmlDocument();
xmlDoc.Load(path + "\\save.xml");

var xmlNodeExist = "Buchhaltung/Customers/CustNo";
var CustNoExist = xdoc.XPathSelectElements(xmlNodeExist).FirstOrDefault(x => (int)x == CustNos);

var SurnameNode = xmlDoc.SelectNodes("Buchhaltung/Customers/Surname");
var ForenameNode = xmlDoc.SelectNodes("Buchhaltung/Customers/Forename");

if (CustNoExist != null)
{
    foreach(XmlNode xn in SurnameNode)
    {
        txtSurnameNew.Text += xn.InnerText + Environment.Newline;
    }

    foreach(XmlNode xn in ForenameNode)
    {
        txtForenameNew.Text += xn.InnerText + Environment.Newline;
    }
}

Hope that will help you. Toby