I am using openxml WordProcessingDocument to open a Word template and replace placeholder x1 with a string. This works fine unless I need the string to contain a newline.
Altough this question is already answered I have another approach to solve questions like :
How can I make XXX with OpenXML??
In this cases you could make use of the powerful Microsoft OpenXML productivity tool (also known as OpenXmlSdkTool). Download here.