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

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();