How to merge two XmlDocuments in C#

Question

I want to merge two XmlDocuments by inserting a second XML doc to the end of an existing Xmldocument in C#. How is this done?

Answer 1

Inserting an entire XML document at the end of another XML document is actually guaranteed to produce invalid XML. XML requires that there be one, and only one "document" element. So, assuming that your files were as follows:

A.xml

   value1
   value2

B.xml

   value3
   value4

The resultant document by just appending one at the end of the other:

   value1
   value2


   value3
   value4

Is invalid XML.

Assuming, instead, that the two documents share a common document element, and you want to insert the children of the document element from B into A's document element, you could use the following:

var docA = new XmlDocument();
var docB = new XmlDocument();

foreach (var childEl in docB.DocumentElement.ChildNodes) {
    var newNode = docA.ImportNode(childEl, true);
    docA.DocumentElement.AppendChild(newNode);
}

This will produce the following document given my examples above:

   value1
   value2
   value3
   value4