После долгих проб и ошибок, вот функция, которая устанавливает текст для узла Word XML и заботится о нескольких строках:
//Sets the text for a Word XML <w:t> node
//If the text is multi-line, it replaces the single <w:t> node for multiple nodes
//Resulting in multiple Word XML lines
private static void SetWordXmlNodeText(XmlDocument xmlDocument, XmlNode node, string newText)
{
//Is the text a single line or multiple lines?>
if (newText.Contains(System.Environment.NewLine))
{
//The new text is a multi-line string, split it to individual lines
var lines = newText.Split("\n\r".ToCharArray(), StringSplitOptions.RemoveEmptyEntries);
//And add XML nodes for each line so that Word XML will accept the new lines
var xmlBuilder = new StringBuilder();
for (int count = 0; count < lines.Length; count++)
{
//Ensure the "w" prefix is set correctly, otherwise docFrag.InnerXml will fail with exception
xmlBuilder.Append("<w:t xmlns:w=\"http://schemas.microsoft.com/office/word/2003/wordml\">");
xmlBuilder.Append(lines[count]);
xmlBuilder.Append("</w:t>");
//Not the last line? add line break
if (count != lines.Length - 1)
{
xmlBuilder.Append("<w:br xmlns:w=\"http://schemas.microsoft.com/office/word/2003/wordml\" />");
}
}
//Create the XML fragment with the new multiline structure
var docFrag = xmlDocument.CreateDocumentFragment();
docFrag.InnerXml = xmlBuilder.ToString();
node.ParentNode.AppendChild(docFrag);
//Remove the single line child node that was originally holding the single line text, only required if there was a node there to start with
node.ParentNode.RemoveChild(node);
}
else
{
//Text is not multi-line, let the existing node have the text
node.InnerText = newText;
}
}