How to remove an element from an xml using Xdocument when we have multiple elements with same name but different attributes

Question

I have an xml document which looks like this:

Answer 1

xd.Descendants("add")
    .First(a => a.Attribute("key").Value == "version")
    .Remove();

If you have tags other than myApp under Applications containing add, you may prefer a safer version

xd.Descendants("myApp").First()
    .Descendants("add")
    .Where(x => (string)x.Attribute("key") == "version")
    .Remove();

---

You can also use XPath (System.Xml.XPath)

string key="version";
xd.XPathSelectElement(String.Format("//myApp/add[@key='{0}']",key)).Remove();

Answer 2

string key = "version";
XDocument xdoc = XDocument.Load(path_to_xml);
xdoc.Descendants("add")
    .Where(x => (string)x.Attribute("key") == key)
    .Remove();

UPDATE You almost did the job. What you missed is filtering elements by attribute value. Here is your code with filtering and removing selected elements:

xd.Element("Applications")
  .Element("myApp")
  .Elements("add")
  .Where(x => (string)x.Attribute("key") == key)
  .Remove();