How to Modify Existing Xml File with Xmldocument and Xmlnode in C#

How to modify existing XML file with XmlDocument and XmlNode in C#

You need to do something like this:

// instantiate XmlDocument and load XML from file
XmlDocument doc = new XmlDocument();
doc.Load(@"D:\test.xml");

// get a list of nodes - in this case, I'm selecting all <AID> nodes under
// the <GroupAIDs> node - change to suit your needs
XmlNodeList aNodes = doc.SelectNodes("/Equipment/DataCollections/GroupAIDs/AID");

// loop through all AID nodes
foreach (XmlNode aNode in aNodes)
{
   // grab the "id" attribute
   XmlAttribute idAttribute = aNode.Attributes["id"];

   // check if that attribute even exists...
   if (idAttribute != null)
   {
      // if yes - read its current value
      string currentValue = idAttribute.Value;

      // here, you can now decide what to do - for demo purposes,
      // I just set the ID value to a fixed value if it was empty before
      if (string.IsNullOrEmpty(currentValue))
      {
         idAttribute.Value = "515";
      }
   }
}

// save the XmlDocument back to disk
doc.Save(@"D:\test2.xml");

Modify xml with Xmldocument in C#

XmlNodeList aNodes returns null because the xml contains these namespace declarations:

<InvoicesDoc xmlns=\"http://www.aade.gr/myDATA/invoice/v1.0\" xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" 
xsi:schemaLocation=\"http://www.aade.gr/myDATA/invoice/v1.0/InvoicesDoc-v0.6.xsd\" 
xmlns:icls=\"https://www.aade.gr/myDATA/incomeClassificaton/v1.0\" 
xmlns:ecls=\"https://www.aade.gr/myDATA/expensesClassificaton/v1.0\">

You need to manage your xml doing something like this:

XmlDocument xml = new XmlDocument();
xml.Load(@"https://www.aade.gr/sites/default/files/2020-09/SampleXML_1.1%20%20%28%CE%A4%CE%99%CE%9C-%CE%A0%CE%A9%CE%9B%CE%97%CE%A3%CE%97%CE%A3_%CE%91%CE%A5%CE%A4%CE%9F%CE%A4%CE%99%CE%9C%29%20.xml");

XmlNamespaceManager manager = new XmlNamespaceManager(xml.NameTable);
            manager.AddNamespace("InvoicesDoc", "http://www.aade.gr/myDATA/invoice/v1.0");

//Example to get the root element
XmlNodeList root = xml.SelectNodes("/InvoicesDoc:InvoicesDoc", manager);

//Example to get the VatNumber tag
XmlNodeList aNodes =xml.SelectNodes("/InvoicesDoc:InvoicesDoc/InvoicesDoc:invoice/InvoicesDoc:issuer/InvoicesDoc:vatNumber", manager);

Modify XML existing content in C#

Well, If you want to update a node in XML, the XmlDocument is fine - you needn't use XmlTextWriter.

XmlDocument doc = new XmlDocument();
doc.Load("D:\\build.xml");
XmlNode root = doc.DocumentElement;
XmlNode myNode = root.SelectSingleNode("descendant::books");
myNode.Value = "blabla";
doc.Save("D:\\build.xml");

C# : Modify a xml node

Try this:

xml.SelectSingleNode("//reminder/Title").InnerText = "NewValue";

Your foreach line is simply looping through a list of elements called "reminders", not it's child nodes.

Take a look at this xpath tutorial for more information:

http://www.w3schools.com/xpath/xpath_intro.asp

How to update node values in XML using C#

Got it!

public static void ReplaceCode()
     {
        var root = new XmlDocument();
         root.Load(@"C:\data.xml");

        foreach (XmlNode e in root.GetElementsByTagName("alternateID"))
        {
            if (e.Attributes["code"].Value.Equals("ALT"))
            {
                e.FirstChild.Value = "00000000"; // FirstChild because the inner node is actually the inner text, yeah XmlNode is weird.
                break;
            }
        }
        root.Save(@"C:\data.xml");
    }

Ask me anything about it and I can clarify. :)

Edit xml file using xmldocument, search by attribute

This should work for you. Your main node already contains element Game - that's why you won't be able to find it in ChildNode. I corrected your main path not to include Game node. So now, you can find it in ChildNodes collection. I added some checks for Node.Name and Attribute name to be sure that it is Game node. It should work for you.

XmlNode node = xdoc["Data"]["Place"]["Date"];
int countvalues = 100;
for (int i = 0; i < countvalues; i++)
{
    foreach (XmlNode childNode in node.ChildNodes)
    {
        if (childNode.Name == "Game" && childNode.Attributes["Name"].InnerText.Equals("Tennis"))
        {
            childNode["balance"].InnerText = xBal.Text;
        }
    }
}

How to change the value of an element in an xml file?

Use LINQ and XDocument:

string applicationName = "Test";
XDocument xdocument = XDocument.Load("Data.xml");
var appName = xdocument.Elements("applicationName").Single();
appName.Value = applicationName;
xdocument.Save("Data.xml");

But you should add System.Xml.Linq to your using directives first.

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