What is the fastest way to combine two xml files into one

Question

If I have two string of xml1 and xml2 which both represent xml in the same format. What is the fastest way to combine these together? The format is not important, but I ju

Answer 1

In my case the main solution did not work well, the difference was that I had a List for a thousands of files when I take one element and try to merge with the first element I get OutOfMemory exception, I added an empty template with and empty row (NodeA in this case) to solve the weird problem of the memory and run smoothly.

I save the document in other process

XDocument xmlDocTemplate = GetXMLTemplate(); -- create an empty document with the same root and empty row element (NodeA), everything will be merge here.
List lstxElements = GetMyBunchOfXML();

foreach (var xmlElement lstxElements)
{
    xmlDocTemplate
        .Root
        .Descendants("NodeA")
        .LastOrDefault()
        .AddAfterSelf(xmlElement.Descendants("NodeA"));
}