c# merge two xml files

using (var output = File.Create(originalFileName))
{
  foreach (var file in new[] { "File1", "File2" })
  {
    using (var input = File.OpenRead(file))
    {
      input.CopyTo(output);
    }
  }
}

var xml1 = XDocument.Load("file1.xml");
var xml2 = XDocument.Load("file2.xml");

//Combine and remove duplicates
var combinedUnique = xml1.Descendants("AllNodes")
                          .Union(xml2.Descendants("AllNodes"));

//Combine and keep duplicates
var combinedWithDups = xml1.Descendants("AllNodes")
                           .Concat(xml2.Descendants("AllNodes"));