Update elements using LINQ to XML?

Question

I have the following XML, but I am having a hard time figuring out how to update the elements directly using LINQ to XML:

XElement settings = XElement.Parse (
@"


 
     
        {USERNAME} 
        {PASSWORD} 
     
  
    {MESSAGEID} 
    {TO} 
    {ACTION} 
     
    {ADDRESS} 
 
   
   
{BODY}
  
");

For example, in the above, I want to access each element that has placholder value {} and update the text. Is doing XElement.Parse() correct in this scenario? I am most likely going to load it into and XDocument first and then update the elements. Also, how could I update attributes, like the Type attribute on Password?

Trying to get to Username, but it says it is an InvalidOperationException.

XNamespace xmlns = "http://schemas.xmlsoap.org/soap/envelope/";
XNamespace wsa = "http://schemas.xmlsoap.org/ws/2004/08/addressing";
XNamespace wsse = "http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd";
XNamespace wsu = "http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd";

var textElement = settings.Elements(xmlns + "Envelope").
                           Elements(xmlns + "Header").
                           Elements(wsse + "Security").
                           Elements(wsse + "UsernameToken").
                           Elements(wsse + "Username").Single();

Also, is it just me or does using XPath seem simpler if I know the exact position of the elements and if I wanted to update or remove xmlns:wsa for example, how would that be achieved?

xanatos · Accepted Answer

This will do it

var elements = settings.DescendantNodes().OfType().Where(p => p.Value.StartsWith("{") && p.Value.EndsWith("}"));

foreach (var node in elements)
{
    // This is an example of manipulation. It will simply remove the {}
    node.Value = node.Value.Substring(1, node.Value.Length - 2);
}

You could move the Where condition directly in the for cycle, like

var elements = settings.DescendantNodes().OfType();

foreach (var node in elements.Where(p => p.Value.StartsWith("{") && p.Value.EndsWith("}")))
{
    // This is an example of manipulation. It will simply remove the {}
    node.Value = node.Value.Substring(1, node.Value.Length - 2);
}

The instruction for finding XText nodes are from XElement value in C#

Note that you'll need to add the missing namespaces:

xmlns:wsse='something' xmlns:wsa='somethingelse' xmlns:wsu='somethingelseelse'

or the XElement.Parse will break;

If you want to update a single element of which you know the name:

XNamespace wsa = "somethingelse"; // Here you must put the namespace!

var textElement = settings.Descendants(wsa + "MessageID").Single(); // If there is only one Message ID to change (0 or > 1 MessageID will make Single throw), .First() if you are only interested in the first one
textElement.Value = "MessageID"; // Changed!

or

var textElements = settings.Descendants(wsa + "MessageID") // If there are multipleMessage ID to change

foreach (var textElement in textElements)
{
    textElement.Value = "MessageID"; // Changed!
}

Be aware that these variants will change the first/all the wsa:MessageID, ignoring their position.

or if you know the exact "path" to your node, use something like

var textElements = settings.Elements(name1).Elements(name2)...

and then use the Single(), the .First() or the foreach

A small sample code:

XElement settings = XElement.Parse(
@"

    
         
             
                {USERNAME} 
                {PASSWORD} 
             
         
        {MESSAGEID} 
        {TO} 
        {ACTION} 
         
            {ADDRESS} 
         
    
    
        {BODY}
    
");


var soapenv = settings.GetNamespaceOfPrefix("soapenv");
var wsa = settings.GetNamespaceOfPrefix("wsa");
var wsse = settings.GetNamespaceOfPrefix("wsse");
var wsu = settings.GetNamespaceOfPrefix("wsu");

XElement username = settings.Elements(soapenv + "Header").Elements(wsse + "Security").Elements(wsse + "UsernameToken").Elements(wsse + "Username").Single();
Console.WriteLine(username);
username.Value = "NewValue";
Console.WriteLine(username);

Update elements using LINQ to XML?

Answers (2)

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